Módulo 6 Med. Interna Flashcards

Question

A 55-year-old Caucasian man consults a physician because of weight loss. He has also had chronic epigastric pain, nausea, and diarrhea. On physical examination, the weight loss is evident and 3+ ankle edema is noted. A complete blood count is unremarkable. Clinical chemistry studies are notable only for a serum albumin of 1.5 g/dL. Endoscopy demonstrates marked thickening of gastric folds in the body of the stomach. Gastric biopsy demonstrates a markedly thickened mucosa, with atrophy of glands accompanied by marked foveal hyperplasia with mucous gland metaplasia in many areas. Which of the following is the most likely diagnosis? (A) Deep gastritis (B) Gastric lymphoma (C) Linitis plastica (D) Menetrier disease (E) Pernicious anemia

Answer 1

**Respuesta: D** The correct **answer is D**. This is Menetrier disease, an uncommon gastric disorder characterized by markedly thickened gastric folds. The disorder is idiopathic, with the gross and microscopic features illustrated in the question stem. Menetrier disease can cause decreased acid secretion (hypochlorhydria) and a protein-losing enteropathy with weight loss and edema secondary to decreased serum albumin that may clinically mimic cancer. Medical treatments are typically ineffective, and some patients require partial or complete gastric resection to control severe hypoalbuminemia. Deep gastritis (**choice A**) is a common form of nonerosive gastritis, usually related to Helicobacter pylori infection. Gastric lymphoma (**choice B**) can also produce markedly thickened rugae, but the microscopic description would mention large numbers of atypical lymphocytes. Linitis plastica (**choice C**) is a term used for an aggressive form of adenocarcinoma in which individual abnormal mucous cells (sometimes with “signet-ring” morphology) penetrate the wall of the stomach and trigger a marked fibrotic reaction. It can also cause thickened rugae. Pernicious anemia (**choice E**) is characterized by marked gastric mucosal atrophy, rather than thickening

Answer 2

**Respuesta: C** The correct **answer is C**. Meningiomas are benign neoplasms of meningothelial origin. They grow from the dura (“dural-based”) toward the cerebral parenchyma, pushing without infiltrating the brain. This pushing pattern of growth, resulting in “welldemarcated” borders, is highly characteristic of any benign neoplasm. An additional MRI/CT feature pointing to meningioma is the presence of a “dural tail” following contrast enhancement. Meningioma is the most frequent of benign CNS tumors and is two times as common in women than in men. Surgical excision is usually easy when located in the cerebral convexities. Rarely, meningiomas may have malignant features, invade the brain, and even result in extracranial metastasis. Meningioma frequently expands into the skull, inducing reactive bone condensation, but this is not a sign of malignancy. Glioblastoma multiforme (GBM) (**choice A**) is the most frequent of primary malignant tumors of the brain. It is an intraaxial tumor (i.e., grows within the brain) and thus can be easily ruled out in this case. GBM is at the most malignant end of the spectrum of astrocytomas, tumors of astrocytic origin. Langerhans cell histiocytosis (**choice B**), in its most frequent monostotic form, produces a single osteolytic lesion within a bone, commonly in the calvarium. A metastasis (**choice D**) may involve any brain structure, including dura mater, but most commonly metastatic disease manifests as multiple brain masses located preferentially at the gray-white matter junction. Paget disease (**choice E**) is a common disease that produces marked thickening and irregularities of bones, especially the calvarium. Pain is a common symptom. It is not associated with an intracranial mass. Schwannoma (**choice F**), like meningioma, is an extraaxial tumor. The great majority of schwannomas originate from the eighth cranial nerve in the cerebellopontine angle. Note that several synonyms are used to designate this tumor (acoustic neuroma or neurinoma is probably the most common). Tuberculoma (**choice G**) is a large aggregate of granulomas due to mycobacterial infection. Rarely, a tuberculoma may develop in the dura mater and simulate a meningioma, but this is definitely an unlikely occurrence.

Answer 3

**Respuesta: D** The correct **answer is D**. The patient is exhibiting typical symptomatology of active tuberculosis, which preferentially affects the posterior segments of the upper lobes. Isoniazid (300 mg/day) prevents active disease in most individuals who are recent “skin test converters,” defined as persons with a prior documented negative tuberculin test within 2 years of a newly positive test. Isoniazid prophylaxis is also recommended for all HIV-positive or immunocompromised patients and for close contacts of patients with active TB. Annual chest x-ray examination (**choice A**) is not an adequate measure to prevent skin converters from developing active tuberculosis and exposes the patient to significant levels of radiation. BCG vaccination (**choice B**) refers to immunization with live attenuated strains of mycobacteria. BCG vaccination is currently recommended in some countries for tuberculin-negative persons, including health professionals, who are repeatedly exposed to patients with tuberculosis. Close observation (**choice C**) would be insufficient to prevent active tuberculosis in a skin test converter. It may be used in the follow-up of close contacts of patients with tuberculosis due to isoniazidresistant strains. Rifampin for 6 months (**choice E**) is also indicated for close contacts of patients with isoniazid-resistant tuberculosis

Answer 4

**Respuesta: E** The correct **answer is E**. The patient’s self-diagnosis of gout is confirmed by his clinical signs and symptoms, family history, and elevated serum uric acid levels. Treatment of the acute attack of gout relies on NSAIDs. Indomethacin has been traditionally used for this purpose, but any of the NSAIDs are equally effective. The treatment should be continued until the symptoms have completely subsided (usually for 1 week). It would be a mistake to begin treatment for acute gout and hyperuricemia at the same time with allopurinol and NSAIDs (**choice A**). If treatment for hyperuricemia is necessary, it should be started after all the acute symptoms have resolved. Rapid reduction of serum uric acid levels can precipitate or worsen acute attacks of gout. Allopurinol acts by inhibiting xanthine oxidase. It is usually administered at an initial dose of 100 mg/day and is increased until the urate level is within normal limits. Aspirin (**choice B**) is contraindicated in gout because it increases serum urate concentration. Colchicine (**choice C**) is effective but causes significant gastrointestinal side effects, such as abdominal cramps and diarrhea. It is therefore reserved for patients who should avoid NSAIDs because of allergies, peptic ulcer disease, or impaired renal function. Intra-articular administration of corticosteroids (**choice D**) may be used to provide prompt relief in acute attacks of monoarticular gout. This treatment is reserved for patients unable to take NSAIDs. The same is true for parenteral administration of corticosteroids (**choice F**), such as IV methylprednisolone, which is otherwise used for polyarticular gout

Answer 5

**Respuesta: A** The correct **answer is A**. This is Caroli disease, complicated by ascending cholangitis. The question stem illustrates a typical presentation of this congenital cystic malformation syndrome of the intrahepatic biliary tree. The disease may also present in early childhood. Associated ascending cholangitis may be difficult to treat; it may also recur and cause hepatic abscesses. Caroli disease strongly predisposes for biliary cirrhosis, and about 10% of these patients develop cholangiocarcinoma (bile duct cancer). About half the patients with Caroli disease also have congenital hepatic fibrosis. Crigler-Najjar syndrome (**choice B**) is an inherited enzymatic abnormality of the liver that causes serious unconjugated hyperbilirubinemia. Dubin-Johnson syndrome (**choice C**) is an inherited enzymatic abnormality that causes a dark gray liver and conjugated hyperbilirubinemia. Gilbert syndrome (**choice D**) is a mild inherited enzymatic disease with asymptomatic unconjugated hyperbilirubinemia. Rotor syndrome (**choice E**) is similar to Dubin-Johnson syndrome, but without the liver discoloration.

Answer 6

**Respuesta: E** The correct **answer is E**. This patient has classic risk factors for pulmonary thromboembolism (PTE): leg injury and bedridden state. Her tachycardia, tachypnea, decreased O2 saturation on pulse oximetry, and lowgrade fever are also consistent with the diagnosis. The chest x-ray is often normal in cases of PTE, as in this patient. Her presenting symptom, delirium, is most likely due to her hypoxic state. Note that PTE is one of the diagnoses the physician is likely to miss if he or she does not actively think about it; this can be fatal to the patient. Shortness of breath is the most common symptom of PTE, and tachypnea is the most frequent sign. In young patients, the common signs and symptoms (cardiac and respiratory) of PTE may mimic anxiety, especially when other corroborating signs are absent. In older patients whose primary complaint is vague chest discomfort, the symptoms might be confused with those of myocardial infarction (MI) (**choice C**), causing the patient to be discharged without further pulmonary work-up after MI is ruled out. At the very least, always suspect PTE when a patient presents with tachycardia and tachypnea and consider ordering a ventilationperfusion (V/Q) scan if suspicions are high. Acute cerebral hemorrhage and acute cerebral infarction (**choices A and B**) might also produce delirium, but one would expect other accompanying neurologic symptoms and signs as well. In addition, a cerebral insult would be less likely to produce this patient’s cardiopulmonary symptoms. The diagnosis of MI (**choice C**) requires satisfying two of the following criteria: history of prolonged chest discomfort, evidence of ischemia or necrosis on ECG (e.g., ST or T wave changes, Q waves), or elevated cardiac enzymes. Pulmonary infarction (**choice D**) usually signifies the presence of a small PTE and typically causes severe pleuritic pain.

Answer 7

**Respuesta: B** The correct **answer is B**. The recent travel history to a malariaendemic region, and especially the sequential occurrence of typical febrile attacks every other day, should alert the physician to the possibility of Plasmodium infection. This parasite should be looked for in peripheral blood smears. Thick blood films are used for detection, whereas thin blood films are used for identification of the Plasmodium species. The number of parasites varies considerably during the course of the disease, and Plasmodium falciparum (the most dangerous) is particularly difficult to detect. Thus, to establish the diagnosis, blood smears should be examined every 8 hours during and between febrile attacks for at least 3 days. Blood cultures (**choice A**) are not useful in this case since Plasmodium parasites cannot be cultured. An ELISA test for P. falciparum has recently become available. Repeating blood smears during an attack (**choice C**) or just once (**choice D**) may not be sufficient to demonstrate Plasmodium parasites in red blood cells. Starting treatment with chloroquine (**choice E**) before establishing diagnosis is not appropriate, although chloroquine is the agent of choice for prophylaxis and therapy of malaria. However, chloroquine-resistant strains of P. falciparum are present throughout the world, including Africa. Patients with falciparum malaria should be hospitalized. In addition, before starting treatment for acute malaria, it is essential to establish whether the patient has received any other antimalarial medication in the previous days to avoid the risk of overdose.

Answer 8

**Respuesta: C** The correct **answer is C**. Acute pancreatitis is most often associated with gallstones and excessive alcohol ingestion. Patients usually present with epigastric pain that radiates to the back, nausea, and vomiting. Examination is significant for fever and tachycardia. Abdominal examination is variable. The diagnosis is established by demonstrating an increase in serum amylase. Serum lipase is also elevated. Leukocytosis and elevated liver enzymes are usually present. Acute cholecystitis (**choice A**) usually begins with colicky pain that progresses and becomes generalized in the right upper quadrant. The classic triad of right upper quadrant pain, fever, and leukocytosis suggests the diagnosis. The patient usually presents with anorexia, nausea, and vomiting. Abdominal examination is significant for right upper quadrant rebound and guarding, as well as distention resulting from a paralytic ileus. Leukocytosis and liver enzyme abnormalities are usually present. The amylase level is normal. Acute gastritis (**choice B**) is usually associated with illness or drugs. The presentation is variable, but patients generally complain of upper abdominal or epigastric pain, nausea, and vomiting. Physical examination is usually normal. Laboratory abnormalities are rare. Guaiac-positive stools may be present if hemorrhage occurs. Intestinal obstruction (**choice D**) usually presents with colicky pain, abdominal distention, and bilious vomiting. Abdominal x-ray films demonstrate distended loops of bowel, air fluid levels, and a paucity of air in the distal colon. Perforated peptic ulcer (**choice E**) presents with severe epigastric pain. Laboratory abnormalities are rare. The diagnosis is easily made by the presence of free intraperitoneal air on abdominal x-ray films

Answer 9

**Respuesta: D** The correct **answer is D**. Schistocytes are small, fragmented, red cells that are formed when red cells squeeze through spaces too small for them and are fragmented. This can happen in myelophthisic anemia, which occurs when tumor, fibrosis, or granulomatous disease obliterates large areas of the marrow cavity. Myelophthisic anemia can be very difficult to treat unless the underlying disease process is controlled, since the marrow simply does not have the necessary volume to produce enough blood cells. Some of these patients will have erythropoiesis in extra-marrow sites such as the spleen or liver. Patients with severe disease are often transfusion dependent. Hypochromic macrocytes (**choice A**) are seen in folate deficiency anemia, vitamin B12 deficiency anemia, and the thalassemias. Nucleated red cells (**choice B**) are immature forms that are seen as a nonspecific finding in many forms of anemia. Ringed sideroblasts (**choice C**) are a feature of sideroblastic anemia, which is a problem with erythrocyte maturation and utilization of iron. Sickled cells (**choice E**) are a feature of sickle cell anemia, and may superficially resemble schistocytes, but are of normal size.

Answer 10

**Respuesta: D** The correct** answer is D**. This patient manifests the classic symptomatology of biliary colic, characterized by pain in the right hypochondrium, which often radiates to the right shoulder. Patients are most often anicteric and afebrile. Virtually all of these cases are due to a gallstone obstructing the cystic duct. If the stone is in the common bile duct, obstructive jaundice becomes a prominent sign. Laparoscopic cholecystectomy is the intervention of choice since the patients can be discharged within 48 hours after surgery, and the procedure is associated with minimal trauma to the abdominal wall. Cheno- or ursodeoxycholic acid treatment (**choice A**) may help dissolve small cholesterol stones and represents an alternative therapy for asymptomatic patients or patients who decline surgery. This treatment is effective only when the gallbladder is functioning. Endoscopic sphincterotomy with stone extraction (**choice C**) may be used for choledocholithiasis, especially in those patients who have already undergone cholecystectomy. Lithotripsy with bile salt treatment (**choice B**) is also an alternative under similar circumstances. Open cholecystectomy (**choice E**) is not the preferred treatment since it is associated with more severe abdominal trauma and longer convalescence compared with the laparoscopic method. However, if any complication should arise during a laparoscopic procedure, the surgeon may easily switch to a more conventional open cholecystectomy

Answer 11

**Respuesta: D** The correct **answer is D**. Approximately 3 to 5% of the distal large bowel cancers are epidermoid carcinoma, with either a nonkeratinizing squamous cell or a basaloid histologic pattern. They can arise in condyloma acuminata (genital warts), which are virally induced proliferations of warts due to infection by HPV. HPV can be transmitted with sexual contact. The more superficial of the epidermoid carcinomas can often be treated with wide excision alone. A combination of chemotherapy and radiation therapy is often successful for somewhat deeper lesions. Herpes simplex I (**choice A**) and II (**choice B**) do not cause cancer. HIV (**choice C**), when it produces clinical AIDS, may predispose to growth of condyloma, but is not itself directly carcinogenic, so HPV is a better answer. The lesions of molluscum contagiosum (**choice E**) are volcano-like skin lesions that do not predispose for cancer. The disorder is caused by a poxvirus

Answer 12

**Respuesta: E** The correct **answer is E**. Herpes simplex virus can produce a fulminant encephalitis that has a tendency to begin in the inferior frontal and medial temporal lobes. This location often leads to behavioral abnormalities as the presenting symptoms, followed by seizures that may be complex partial, as in this case, or generalized tonic-clonic. Imaging may be initially normal, but MRI subsequently demonstrates inflammation in the medial temporal and inferior frontal lobes. The CSF profile shows a lymphocytic pleocytosis with some evidence of a hemorrhagic component. EEG may show periodic focal spikes on a background of slow or lowamplitude (“flattened”) activity. Bacterial meningitis (**choice A**) typically causes meningismus and should show a neutrophil-predominant CSF profile with a decreased glucose. Brain abscess (**choice B**) typically presents with high fever, headaches, focal neurologic complaints, and seizures. A head CT with contrast should demonstrate a ring-enhancing lesion with edema and mass effect. Creutzfeldt-Jakob disease (**choice C**), a degenerative dementia caused by infective prion proteins, can present with behavioral symptoms but follows a more subacute course. The CSF is usually unremarkable. Infarcts may rarely present with behavioral symptoms and no focal features, but a 2-day-old hemorrhagic infarct (**choice D**) would be apparent on a CT.

Answer 13

**Respuesta: B** The correct **answer is B**. The patient has colon cancer. It is important before many cancer surgeries to measure serum levels of appropriate tumor markers, since elevation of these markers before surgery indicates that they can then be used for monitoring disease recurrence. In the case of colon cancer, appropriate markers include CEA, CA 19-9, and CA 125. CEA is actually a nonspecific marker for many solid tumors, but is particularly useful in colon cancer, where it is commonly elevated. AFP (**choice A**) is a marker for liver, ovary, and testicular cancer. hCG (**choice C**) is produced by many tumors but is not as good as CEA for colon cancer. PSA (**choice D**) is a marker for prostate cancer, although it is increased in benign prostatic hyperplasia as well. TSH (**choice E**) is produced by some choriocarcinomas

Answer 14

**Respuesta: C** The correct **answer is C**. This is the typical clinical presentation of primary atypical pneumonia, which is most frequently caused by Mycoplasma pneumoniae, and less frequently by viruses (influenza, respiratory syncytial virus, adenovirus, rhinoviruses, rubeola, and varicella virus), Chlamydia, or Coxiella burnetii. What differentiates primary atypical pneumonia from other forms of acute pneumonia is the predominantly interstitial, rather than intra-alveolar, inflammation and scarcity of “localizing” symptoms. M. pneumoniae infections are often associated with circulating cold agglutinins. Small outbreaks within close communities are characteristic of pneumonia due to this microorganism. Erythromycin is the drug of choice. Influenza virus (**choice A**) causes infection in an epidemic pattern. The symptoms begin rapidly, with sore throat, nasal stuffiness, fever, chills, and muscle aches. Leukopenia is commonly seen. Superimposed bacterial pneumonia is frequent in chronically ill individuals and the elderly. In young people, influenza is usually a self-limiting disease that lasts approximately 1 week. Mixed anaerobic bacteria (**choice B**) are responsible for cases of pneumonia associated with lung cavitation (abscess) and clinically manifesting with cough productive of foul-smelling sputum. There are usually predisposing conditions, such as poor dental hygiene or situations favoring aspiration. Pneumocystis carinii (**choice D**) is a fungus that causes pneumonia in severely immunocompromised hosts, especially AIDS patients. The clinical picture is severe. Symptoms begin abruptly, with high fever, chills, malaise, and shortness of breath. Acute respiratory failure ensues if appropriate therapy (trimethoprimsulfamethoxazole) is not instituted. Streptococcus pneumoniae (**choice E**) is the most common etiologic agent of community-acquired pneumonia, resulting in consolidation of a single lobe and high fever with rigors, productive cough, and profound malaise.

Answer 15

**Respuesta: C** The correct **answer is C**. Magnesium deficiency usually results from inadequate intake coupled with defective renal or gut absorption. Chronic alcoholism is an important clinical cause of magnesium deficiency in the U.S., probably because of both inadequate intake and excessive renal excretion. Alcoholism may also affect calcium and potassium metabolism. Hypomagnesemia may also be seen in malabsorption, kwashiorkor, parathyroid disease (particularly after removal of a parathyroid tumor), and chronic diarrhea. Manifestations include anorexia, nausea, vomiting, lethargy, weakness, seizures, and tetany. Iodine deficiency (**choice A**) can cause thyroid dysfunction with goiter. Iron deficiency (**choice B**) can cause microcytic anemia, glossitis, and esophageal webs. Selenium deficiency (**choice D**) is very rare but can cause cardiomyopathy. Zinc deficiency (**choice E**) can cause growth retardation, night blindness, and skin and hair changes.

Answer 16

**Respuesta: E** The correct **answer is E**. Hepatomegaly, arthralgias, and skin hyperpigmentation (which may give the characteristic “bronze” color) are among the most common initial signs of hemochromatosis. Testicular atrophy is often present as well. Hemochromatosis leads to iron overload affecting the whole organism, but the liver, heart, pancreas, and endocrine glands bear the most injurious effects of iron deposition. Thus, cardiomyopathy and diabetes frequently manifest because of myocardial and pancreatic damage. A gallop rhythm, with associated S3 sound, is evidence of cardiomegaly. Note the high ferritin levels and elevated transferrin saturation, indicating systemic iron overload. This disease is due to an autosomal recessive mutation of a gene (named HFE) encoding a protein that interacts with beta-2-microglobulin. The ensuing pathogenetic steps are still unclear. When hemochromatosis is suspected, the definitive diagnostic confirmation relies on determination of iron content in liver biopsies. Histologic evaluation of iron deposition is not sufficiently accurate. CT or MRI studies of the liver (**choice A**) may demonstrate iron overload in the liver, but these radiologic methods are not sensitive. Measurement of serum alpha-1-antitrypsin (**choice B**) is undertaken when alpha-1-antitrypsin deficiency is suspected. In this case, liver damage and other signs and symptoms indicate iron overload as the most likely underlying etiology. Measurement of urinary copper excretion (**choice C**) is the initial diagnostic method of choice, together with ceruloplasmin serum levels, in the diagnosis of Wilson disease, because of excessive copper accumulation in liver and other organs. Serum titers of antinuclear and antimitochondrial antibodies (**choice D**) are elevated in 90 to 95% of patients with primary biliary cirrhosis. These patients usually present with generalized pruritus, presumably secondary to retention of bile salts.

Answer 17

**Respuesta: B** The correct **answer is B**. This is one of those “higher cognitive level” questions that bypasses the diagnosis and goes directly to management, on the logical assumption that unless you have made a tentative diagnosis, you cannot select the appropriate treatment. Here the clinical diagnosis is prolactinoma, from a pituitary microadenoma (too small to produce visual field defects). The first line of treatment is bromocriptine. Pituitary surgery can be performed if needed. Bilateral mastectomy (**choice A**) would indeed wipe out milk production, but it would do so in a mutilating, totally unnecessarily radical way. The breasts are normal; all we need to do is stop their stimulation by prolactin. Streptozocin (**choice C**) is the chemotherapeutic agent of choice when the islands of Langerhans have to be destroyed. Thus, it is indicated for inoperable tumors producing gastrin, insulin, or glucagon. **Choices D and E** are offered for those who mistakenly assumed that abnormal milk production is a sign of advanced breast cancer. It is not.

Answer 18

**Respuesta: A** The correct **answer is A**. Among hypertensive intra-cerebral bleeds, cerebellar hematomas merit special consideration. A hematoma within a cerebellar hemisphere manifests with sudden onset of headache and ataxia in an otherwise lucid patient. This highly characteristic presentation warrants immediate medical attention because of the possibility of full recovery if properly treated. An intracerebral hematoma in the cerebral white matter (**choice B**) is usually accompanied by lateralized motor and/or sensory deficits. Epidural hemorrhage (**choice C**) is always of traumatic origin and manifests with the characteristic talk-and-die syndrome. There is a lucid interval between trauma and coma. Following hemorrhages in the pons (**choice D**), the patient falls into immediate coma with quadriparesis and usually dies of cardiorespiratory arrest. The putamen (**choice E**) is the most frequent site of hypertensive bleeding. Putamenal hemorrhage usually involves the adjacent internal capsule, leading to contralateral hemiparesis, hemianesthesia, and hemianopia. Bleeding into the thalamus (**choice F**) may be suspected when the patient manifests hemianesthesia that precedes hemiparesis.

Answer 19

**Respuesta: D** The correct **answer is D**. With the progress of necrotizing fasciitis, the tenderness may evolve to anesthesia, as cutaneous nerves are infarcted. Surgery for debridement and fasciotomy is needed for diagnosis and treatment because the infection is extensive and rapidly progressive. Once the surgery is complete, antibiotics must be continued. This patient has a shock-like syndrome that is the result of the pyrogenic exotoxin A produced by the bacteria. Clindamycin (**choice A**) arrests the production of the exotoxin. Surgery is of paramount importance, however. Erythromycin (**choice B**) may be used if the patient had a penicillin allergy. Penicillin G (**choice C**) is also adjunctive therapy because surgery is of paramount importance. If the patient becomes progressively hypotensive and risks hemodynamic collapse, vasopressors may be needed (**choice E**). But, fluid resuscitation should be attempted first.

Answer 20

**Respuesta: A** The correct **answer is A.** Given this patient’s extensive sunlight exposure, she most likely has a basal cell carcinoma. This is the most common form of skin cancer. Risk factors include sun exposure and ultraviolet radiation. Excision may be needed to avoid metastasis. Erythema nodosum (**choice B**) is a vascular disorder. Skin manifestations include erythematous and nodular lesions, typically on the anterior aspect of the tibia. Leukoplakia (**choice C**) is caused by the Epstein-Barr virus. It is found on the lateral aspects of the tongue and is white in appearance. Melanoma (**choice D**) has the maximum metastatic potential and may be nodular or radial. It may have irregular borders, may be of variegated coloration, be >4 mm in size, and be on any aspect of the body. Squamous cell carcinoma (**choice E**) is the second most common form of skin cancer. They commonly occur on the lower lip.

Answer 21

**Respuesta: E** The correct **answer is E**. This patient has the signs and symptoms of obstructive sleep apnea. This condition is characterized by poor nighttime sleeping resulting in daytime somnolence and the psychological consequences of prolonged sleep deprivation. Patients tend to be irritable, have difficulty concentrating on daytime tasks, and have an inappropriate lack of energy given their activity level. Although only 50% of obstructive sleep apnea patients are obese, obese patients tend to have an increased amount of redundant nasal and nasopharyngeal tissue, which makes their upper airway more likely to obstruct in the supine position. Diagnosis of obstructive sleep apnea is initially made by the appropriate history and symptoms and is confirmed by polysomnography, or sleep study, which documents apnea or hypopnea in addition to oxygen desaturations during these obstructive episodes. Empiric trial of weight loss and exercise (**choice A**) is part of the treatment plan in patients who have obstructive sleep apnea, but it does not confirm the diagnosis. Also, anatomic abnormalities independent of the increase in soft tissues associated with obesity may be the source of the problem, which would not resolve with weight loss or exercise. Laboratory tests for hypothyroidism (**choice B**) are not indicated at this time, given the lack of other symptoms consistent with a diagnosis of hypothyroidism. Mask continuous positive airway pressure (CPAP) (**choice C**) should not be administered unless the patient has been evaluated clinically for the presence of obstructive sleep apnea, either with polysomnography or continuous oxygen saturation measurements. In addition, CPAP administration will not be funded without documented evidence of sleep apnea. An MRI of the head and neck for soft tissues (**choice D**) is not indicated and may not provide any information regarding the pathology of the insomnia. In addition, obstructive sleep apnea is a dynamic process that would need to be viewed radiologically in real time. The presence of redundant soft tissues in the nasopharynx and oropharynx does not necessarily confirm the diagnosis of obstructive sleep apnea.

Answer 22

**Respuesta: G** The correct **answer is G**. In this case, oliguria and other signs of acute renal failure may result from either sustained hypotension (secondary to fluid loss) or acute tubular necrosis. The latter may result from hypoxic/ischemic damage to the tubular cells in the setting of shock or sepsis. Thus, prerenal azotemia is due to decreased renal perfusion, whereas renal azotemia is due to intrinsic damage to renal tubules. The treatment differs depending on the underlying cause. The parameters that allow the differential diagnosis between prerenal and renal azotemia are principally the fractional excretion of sodium (FRNa) and the ratio between BUN and serum creatinine. Renal failure due to hypovolemic shock, as in this case, will manifest with prerenal azotemia, associated with FRNa <1% and BUN:Cr ratio >20. Usually, urine is hyperosmolar compared with plasma. Cardiogenic shock (**choice C**) may also give rise to acute renal failure because of prerenal azotemia (hypoperfusion). In this case, however, the most likely mechanism is hypovolemic shock secondary to loss of fluid. However, acute renal failure secondary to radiographic contrast toxicity (**choice M**) develops within 24 h after administration of IV radiocontrast. Further, it is obvious that anuria in this case is due to obstruction, not to intrinsic renal damage. Aminoglycoside toxicity (**choice A**) is a common cause of acute renal failure due to acute tubular necrosis, in which case FRNa is >1% since damaged tubular cells are unable to reabsorb sodium. In addition, the BUN:Cr ratio is <20, and urine osmolality approaches that of the plasma (250-300 mOsmol/kg). Analgesic toxicity (**choice B**) is due to chronic ingestion of large amounts of such agents as NSAIDs, aspirin, and paracetamol. It may result in papillary necrosis and progressive renal interstitial damage. Such damage will eventually lead to chronic interstitial nephritis, manifesting with chronic renal failure. Polyuria due to inability of the kidneys to concentrate urine is a typical early sign. Goodpasture syndrome (**choice D**) is a chronic inflammatory disorder affecting the lungs and kidneys. It is mediated by antibodies against the collagen of the basement membranes of the lungs and glomeruli. Hemoptysis and nephritic syndrome often progressing to renal failure are its clinical manifestations. Henoch-Schönlein purpura (**choice E**) is a disease of children. Purpura, hematuria, abdominal pain, melena, and arthralgias constitute its clinical picture, and IgA-mediated vasculitis its pathologic substrate. Hyperuricemia (**choice F**) may cause acute renal failure, which develops in patients with rapid cell turnover, namely patients with leukemia or lymphoma who are undergoing chemotherapy. Malignant hypertension (**choice H**) may cause hematuria, proteinuria, and loss of renal function because of arteriolar damage. Blood pressure is very high, usually >220/120 mm Hg. Multiple myeloma (**choice I**) is a plasma cell neoplasia associated with production of a monoclonal immunoglobulin. Fragments of this immunoglobulin (usually dimers of light chains) are filtered through the glomerulus and may precipitate in the tubules. This will result in proteinuria, hypertension, and progressive renal failure. Myoglobinuria (**choice J**) may produce acute tubular necrosis in the setting of extensive crush injuries that cause necrosis of skeletal muscle. Postinfectious glomerulonephritis (**choice K**) usually follows pharyngitis or impetigo due to group A Streptococcus and manifests with typical nephritic syndrome. Rarely, this condition may manifest with rapidly progressive glomerulonephritis (i.e., crescentic type), leading to acute RF. Sickle cell disease (**choice N**) is one of the causes of renal papillary necrosis. Other causes include analgesic toxicity, obstructive uropathy with recurrent urinary tract infections, and diabetes. Unilateral ureteral stone (**choice O**) would manifest with acute onset of colicky flank pain, associated with gross or microscopic hematuria. Acute renal failure does not ensue in this situation, unless the contralateral kidney is already impaired.

Answer 23

**Respuesta: L** The correct **answer is L**. The clinical picture is consistent with acute urinary retention secondary to prostatic hyperplasia, which is an example of postrenal azotemia. Acute onset of anuria is usually accompanied by signs of acute renal failure, i.e., nausea and vomiting, malaise, and obtunded sensorium. This acute clinical picture is usually preceded by a long history of urinary symptoms due to prostatic hyperplasia, namely progressively increasing hesitancy, decreased force of stream, and postvoid dribbling. Use of drugs with anticholinergic properties, such as tricyclic antidepressants, may precipitate acute urinary retention. The recent history of intravenous pyelography (IVP) should not mislead you. Radiologic contrast media may act as direct nephrotoxins. Cardiogenic shock (**choice C**) may also give rise to acute renal failure because of prerenal azotemia (hypoperfusion). In this case, however, the most likely mechanism is hypovolemic shock secondary to loss of fluid. However, acute renal failure secondary to radiographic contrast toxicity (**choice M**) develops within 24 h after administration of IV radiocontrast. Further, it is obvious that anuria in this case is due to obstruction, not to intrinsic renal damage. Aminoglycoside toxicity (**choice A**) is a common cause of acute renal failure due to acute tubular necrosis, in which case FRNa is >1% since damaged tubular cells are unable to reabsorb sodium. In addition, the BUN:Cr ratio is <20, and urine osmolality approaches that of the plasma (250-300 mOsmol/kg). Analgesic toxicity (**choice B**) is due to chronic ingestion of large amounts of such agents as NSAIDs, aspirin, and paracetamol. It may result in papillary necrosis and progressive renal interstitial damage. Such damage will eventually lead to chronic interstitial nephritis, manifesting with chronic renal failure. Polyuria due to inability of the kidneys to concentrate urine is a typical early sign. Goodpasture syndrome (**choice D**) is a chronic inflammatory disorder affecting the lungs and kidneys. It is mediated by antibodies against the collagen of the basement membranes of the lungs and glomeruli. Hemoptysis and nephritic syndrome often progressing to renal failure are its clinical manifestations. Henoch-Schönlein purpura (**choice E**) is a disease of children. Purpura, hematuria, abdominal pain, melena, and arthralgias constitute its clinical picture, and IgA-mediated vasculitis its pathologic substrate. Hyperuricemia (**choice F**) may cause acute renal failure, which develops in patients with rapid cell turnover, namely patients with leukemia or lymphoma who are undergoing chemotherapy. Malignant hypertension (**choice H**) may cause hematuria, proteinuria, and loss of renal function because of arteriolar damage. Blood pressure is very high, usually >220/120 mm Hg. Multiple myeloma (**choice I**) is a plasma cell neoplasia associated with production of a monoclonal immunoglobulin. Fragments of this immunoglobulin (usually dimers of light chains) are filtered through the glomerulus and may precipitate in the tubules. This will result in proteinuria, hypertension, and progressive renal failure. Myoglobinuria (**choice J**) may produce acute tubular necrosis in the setting of extensive crush injuries that cause necrosis of skeletal muscle. Postinfectious glomerulonephritis (**choice K**) usually follows pharyngitis or impetigo due to group A Streptococcus and manifests with typical nephritic syndrome. Rarely, this condition may manifest with rapidly progressive glomerulonephritis (i.e., crescentic type), leading to acute RF. Sickle cell disease (**choice N**) is one of the causes of renal papillary necrosis. Other causes include analgesic toxicity, obstructive uropathy with recurrent urinary tract infections, and diabetes. Unilateral ureteral stone (**choice O**) would manifest with acute onset of colicky flank pain, associated with gross or microscopic hematuria. Acute renal failure does not ensue in this situation, unless the contralateral kidney is already impaired.

Answer 24

**Respuesta: G** The correct **answer is G**. These clinical manifestations, especially the characteristics of the systolic murmur, are consistent with aortic stenosis, which is often associated with anginal pain. The patient also shows signs of impeding left ventricular failure, namely exertional dyspnea and left ventricular hypertrophy. Aortic stenosis manifesting in younger individuals (<50 years) is usually due to a congenitally abnormal aortic valve. In the elderly, calcification of aortic valve cusps is the most common cause. Acute cholecystitis (**choice A**) manifests with abdominal pain in the right upper quadrant radiating to the back and right shoulder, fever, and leukocytosis. Occasionally, it may present with precordial pain. Acute pericarditis (**choice B**) is associated with precordial pain, fever, and evidence of pericardial effusion, e.g., a pericardial rub. If pericardial effusion is abundant, cardiac tamponade may ensue. Acute pleuritis (**choice C**) is characterized by lateralized chest pain that intensifies with deep breathing. Objective signs of pleural effusion, as well as a pleuritic rub, are usually present. Angina pectoris (**choice D**), in its most common form, manifests with precordial pain that has a crushing or squeezing quality. The pain is triggered by exercise or emotional stress and relieved by rest or vasodilators. Aortic dissection (**choice E**) is an emergency manifesting with excruciating chest pain radiating to the back, pulse and pressure discrepancies, onset of aortic regurgitation, and shock. A history of hypertension is often present. Aortic regurgitation (**choice F**) is associated with a diastolic murmur and a wide differential between systolic and diastolic pressure. Costochondritis (**choice H**), also known as Tietze syndrome, is due to inflammation of the chondrocostal junctions, which are swollen and sore. Esophageal carcinoma (**choice I**) may produce chest pain but usually manifests with progressive dysphagia, anorexia, and weight loss. Alcohol and smoking habits are often present in the history. Esophageal spasm (**choice J**) is a rare cause of chest pain, but it is usually associated with swallowing difficulties. An x-ray after barium may show evidence of spasm. Herpes zoster (**choice K**) is characterized by a vesicular eruption along a dermatome, which may be followed by chronic burning pain, especially in elderly patients. Mitral valve prolapse (**choice L**) is due to myxomatous degeneration of mitral valve leaflets. It results in a characteristic midsystolic click followed, in the more severe cases, by a regurgitation murmur. Myocardial infarction (**choice M**) usually results in extremely severe chest pain radiating to the left shoulder. The pain typically lasts longer than 30 minutes and is not relieved by rest or vasodilators. Many exceptions exist to this classic presentation, such as painless infarction or pain with unusual localization or radiation. Myocarditis (**choice N**) may be asymptomatic, or it may lead to the acute onset of arrhythmias and acute heart failure or the late onset of slowly progressive congestive heart failure. Pneumonia (**choice O**) may cause chest pain along with cough, sputum production, and fever. Pulmonary infiltrates are present on chest x-ray. Prinzmetal angina (**choice P**) characteristically manifests with precordial pain in the early morning and results from coronary vasospasm without atherosclerotic stenosis. Psychological chest pain (**choice Q**) is commonly associated with underlying depressive, anxiety, or panic disorders. Pulmonary thromboembolism (**choice R**) usually occurs in the setting of predisposing conditions and manifests with chest pain, respiratory distress, tachypnea, and tachycardia. These symptoms, however, may be mild and difficult to interpret. Chest x-ray films and ventilation-perfusion scans are mandatory in any patient with suspicious signs. Secondary pneumothorax (**choice T**), in contrast to the spontaneous form, develops in lungs with preexisting alterations, most commonly in chronic obstructive pulmonary disease (COPD). COPD leads to formation of subpleural bullae that may rupture. Abrupt onset of pain and worsening of dyspnea develop. Thoracic outlet syndrome (**choice V**) originates from anatomic or inflammatory alterations of the thoracic outlet (a cervical rib, for example), which may result in compression or irritation of the neurovascular bundle. Pain is triggered by movements of the upper extremity or shoulder and is associated with paresthesias and muscle weakness.

Answer 25

**Respuesta: U** The correct **answer is U**. The clinical history and objective findings are highly characteristic of spontaneous (primary) pneumothorax, which often affects tall, thin men between 20 and 40 years of age. Chest pain and respiratory distress begin suddenly, usually at rest and often during sleep. Patients often seek medical attention days after the onset of symptoms. If the pneumothorax is large, diminished breath sounds, reduced tactile fremitus, and hyperresonance are present. The condition is thought to arise from spontaneous rupture of subpleural bullae in otherwise normal lungs. Acute cholecystitis (**choice A**) manifests with abdominal pain in the right upper quadrant radiating to the back and right shoulder, fever, and leukocytosis. Occasionally, it may present with precordial pain. Acute pericarditis (**choice B**) is associated with precordial pain, fever, and evidence of pericardial effusion, e.g., a pericardial rub. If pericardial effusion is abundant, cardiac tamponade may ensue. Acute pleuritis (**choice C**) is characterized by lateralized chest pain that intensifies with deep breathing. Objective signs of pleural effusion, as well as a pleuritic rub, are usually present. Angina pectoris (**choice D**), in its most common form, manifests with precordial pain that has a crushing or squeezing quality. The pain is triggered by exercise or emotional stress and relieved by rest or vasodilators. Aortic dissection (**choice E**) is an emergency manifesting with excruciating chest pain radiating to the back, pulse and pressure discrepancies, onset of aortic regurgitation, and shock. A history of hypertension is often present. Aortic regurgitation (**choice F**) is associated with a diastolic murmur and a wide differential between systolic and diastolic pressure. Costochondritis (**choice H**), also known as Tietze syndrome, is due to inflammation of the chondrocostal junctions, which are swollen and sore. Esophageal carcinoma (**choice I**) may produce chest pain but usually manifests with progressive dysphagia, anorexia, and weight loss. Alcohol and smoking habits are often present in the history. Esophageal spasm (**choice J**) is a rare cause of chest pain, but it is usually associated with swallowing difficulties. An x-ray after barium may show evidence of spasm. Herpes zoster (**choice K**) is characterized by a vesicular eruption along a dermatome, which may be followed by chronic burning pain, especially in elderly patients. Mitral valve prolapse (**choice L**) is due to myxomatous degeneration of mitral valve leaflets. It results in a characteristic midsystolic click followed, in the more severe cases, by a regurgitation murmur. Myocardial infarction (**choice M**) usually results in extremely severe chest pain radiating to the left shoulder. The pain typically lasts longer than 30 minutes and is not relieved by rest or vasodilators. Many exceptions exist to this classic presentation, such as painless infarction or pain with unusual localization or radiation. Myocarditis (**choice N**) may be asymptomatic, or it may lead to the acute onset of arrhythmias and acute heart failure or the late onset of slowly progressive congestive heart failure. Pneumonia (**choice O**) may cause chest pain along with cough, sputum production, and fever. Pulmonary infiltrates are present on chest x-ray. Prinzmetal angina (**choice P**) characteristically manifests with precordial pain in the early morning and results from coronary vasospasm without atherosclerotic stenosis. Psychological chest pain (**choice Q**) is commonly associated with underlying depressive, anxiety, or panic disorders. Pulmonary thromboembolism (**choice R**) usually occurs in the setting of predisposing conditions and manifests with chest pain, respiratory distress, tachypnea, and tachycardia. These symptoms, however, may be mild and difficult to interpret. Chest x-ray films and ventilation-perfusion scans are mandatory in any patient with suspicious signs. Secondary pneumothorax (**choice T**), in contrast to the spontaneous form, develops in lungs with preexisting alterations, most commonly in chronic obstructive pulmonary disease (COPD). COPD leads to formation of subpleural bullae that may rupture. Abrupt onset of pain and worsening of dyspnea develop. Thoracic outlet syndrome (**choice V**) originates from anatomic or inflammatory alterations of the thoracic outlet (a cervical rib, for example), which may result in compression or irritation of the neurovascular bundle. Pain is triggered by movements of the upper extremity or shoulder and is associated with paresthesias and muscle weakness.

Answer 26

**Respuesta: S** The correct **answer is S**. Despite the vague familial history of heart problems, the clinical symptomatology is classic for gastroesophageal reflux or reflux esophagitis. The onset of pain in the recumbent position and soon after meals, along with the relief provided by antacids or milk, is virtually diagnostic. Upper endoscopy is the diagnostic procedure of choice to establish a definitive diagnosis and to obtain biopsy specimens of the esophageal mucosa. Acute cholecystitis (**choice A**) manifests with abdominal pain in the right upper quadrant radiating to the back and right shoulder, fever, and leukocytosis. Occasionally, it may present with precordial pain. Acute pericarditis (**choice B**) is associated with precordial pain, fever, and evidence of pericardial effusion, e.g., a pericardial rub. If pericardial effusion is abundant, cardiac tamponade may ensue. Acute pleuritis (**choice C**) is characterized by lateralized chest pain that intensifies with deep breathing. Objective signs of pleural effusion, as well as a pleuritic rub, are usually present. Angina pectoris (**choice D**), in its most common form, manifests with precordial pain that has a crushing or squeezing quality. The pain is triggered by exercise or emotional stress and relieved by rest or vasodilators. Aortic dissection (**choice E**) is an emergency manifesting with excruciating chest pain radiating to the back, pulse and pressure discrepancies, onset of aortic regurgitation, and shock. A history of hypertension is often present. Aortic regurgitation (**choice F**) is associated with a diastolic murmur and a wide differential between systolic and diastolic pressure. Costochondritis (**choice H**), also known as Tietze syndrome, is due to inflammation of the chondrocostal junctions, which are swollen and sore. Esophageal carcinoma (**choice I**) may produce chest pain but usually manifests with progressive dysphagia, anorexia, and weight loss. Alcohol and smoking habits are often present in the history. Esophageal spasm (**choice J**) is a rare cause of chest pain, but it is usually associated with swallowing difficulties. An x-ray after barium may show evidence of spasm. Herpes zoster (**choice K**) is characterized by a vesicular eruption along a dermatome, which may be followed by chronic burning pain, especially in elderly patients. Mitral valve prolapse (**choice L**) is due to myxomatous degeneration of mitral valve leaflets. It results in a characteristic midsystolic click followed, in the more severe cases, by a regurgitation murmur. Myocardial infarction (**choice M**) usually results in extremely severe chest pain radiating to the left shoulder. The pain typically lasts longer than 30 minutes and is not relieved by rest or vasodilators. Many exceptions exist to this classic presentation, such as painless infarction or pain with unusual localization or radiation. Myocarditis (**choice N**) may be asymptomatic, or it may lead to the acute onset of arrhythmias and acute heart failure or the late onset of slowly progressive congestive heart failure. Pneumonia (**choice O**) may cause chest pain along with cough, sputum production, and fever. Pulmonary infiltrates are present on chest x-ray. Prinzmetal angina (**choice P**) characteristically manifests with precordial pain in the early morning and results from coronary vasospasm without atherosclerotic stenosis. Psychological chest pain (**choice Q**) is commonly associated with underlying depressive, anxiety, or panic disorders. Pulmonary thromboembolism (**choice R**) usually occurs in the setting of predisposing conditions and manifests with chest pain, respiratory distress, tachypnea, and tachycardia. These symptoms, however, may be mild and difficult to interpret. Chest x-ray films and ventilation-perfusion scans are mandatory in any patient with suspicious signs. Secondary pneumothorax (**choice T**), in contrast to the spontaneous form, develops in lungs with preexisting alterations, most commonly in chronic obstructive pulmonary disease (COPD). COPD leads to formation of subpleural bullae that may rupture. Abrupt onset of pain and worsening of dyspnea develop. Thoracic outlet syndrome (**choice V**) originates from anatomic or inflammatory alterations of the thoracic outlet (a cervical rib, for example), which may result in compression or irritation of the neurovascular bundle. Pain is triggered by movements of the upper extremity or shoulder and is associated with paresthesias and muscle weakness.