NBME 12 Flashcards
A patient treated for bone marrow transplantation presents with interstitial pneumonia. What is the most likely cause and what deficiency resulted in this? What may be seen on histology?
CMV -> T-lymphocyte deficiency
OWL EYE NUCLEI
What are the renal compensatory mechanisms in diabetic ketoacidosis?
- Increased bicarb reabsorption (to combat anion gap metabolic acidosis) -> decreased urine bicarb
- Increased H+ excretion -> decreased urine pH
- Increased acid buffer (ammonia and phosphate) excretion to maintain H+ excretion -> Increased urine NH4+ and H2PO4-
What does parietal cell loss predispose a patient to?
Pernicious ANEMIA!!
because loss of IF -> no B12 absorption
A patient presents with signs of peptic ulcer disease and elevated serum gastrin levels, what is the most likely cause of this and best treatment option?
Zollinger-Ellinson syndrome (gastrinoma) - gastrin secreting tumor
PPIs are the best option!
How do you calculate the Km of an enzyme?
Amount of substrate at 1/2 Vmax
Where do the short gastric arteries branch from, and where do they anastamose? What disease can affect these arteries?
Branch of splenic artery, with POOR anastamoses, so gastric veins drain into splenic vein
Portal hypertension would also cause splenic and hence short gastric vein hypertension
What kind of drug is chlordiazepoxide and what would result from severe overdose? What would you see on ABG?
Med-long acting benzodiazepine -> can cause confusion, hypotension, hypoventilation, coma
Resp Depression -> Decrease pO2 and Increase pCO2 -> Decrease pH
Where is ACE primarily active leading to increased release of ATII from this location?
Pulmonary vasculature and Renal epithelial cells
What are the endothelial and PMN surface proteins involved in each step of leukocyte adhesion and extravasation?
- Margination and rolling -> SELECTINS on vessel bind Sialyl-Lewis on PMNs (selectins on the vessel select the PMN)
- Tight binding -> ICAM and VCAM on vessel bind INTEGRINS on PMN (Cams catch PMN, which INTEGRATE with the vessel)
- Diapedesis -> PECAM1 on vessel bind PECAM1 on PMN
- Migration -> chemotactic molecules - C5a, IL8, LTB4, kallikrein, platelet activating factor, bacterial products
What is ehrlichiosis, and how do you treat it?
Tickborne bacterial infection caused by the anaplasma and ehrlichia families
Tx: Doxycycline - binds 30s ribosome and prevents tRNA attachment
How will a patient with Klinefelter syndrome present?
Male - 47 XXY
- TESTICULAR ATROPHY!! -> azoospermia -> infertility
- Tall, thin, long extremeties, gynecomastia, female hair distributio, inactivated X chromosomes (bar bodies)
Which cells use insulin dependent glucose transporters? What would be the rate of glucose uptake as serum glucose increases without insulin?
GLUT4 - Adipose tissue, striated muscle
No increase in rate of glucose uptake without insulin
What effect does insulin have in the kidneys and muscles?
Kidneys -> increased Na+ retention
Muscles -> increased glucose uptake and increased protein synthesis
What are the signs of premature (primary) ovarian failure?
Amenorrhia + signs of menopause (after puberty but before age 40) with decrease estrogen and INCREASED LH and FSH
Premature atresia of ovarian follicles
What is the pathogenesis for immune thrombocytopenia purpura? What would the lab values and bone marrow biopsy reveal?
Anti-GpIIb/IIIa antibodies -> splenic macrophage consumption of platelet-Ab complex -> Decreased platelet count -> Increased bleeding time -> mucosal bleeding, epistaxis, petechiae, purpura
Increased megakaryocytes on bone marrow biopsy
What are the normal PT and PTT?
PT = 11-15 sec PTT = 25 - 40 sec
What allows helicobacter pylori to persist in the acidic gastric and duodenal mucosa?
- Uses flagella to burrow into the mucosa epithelial cells where pH is more neutral
- UREASE breaks down urea in the stomach into CO2 and ammonia which neutralizes acid surrounding bacterium
What are the main catalase+ organisms?
“Cats Need PLACESS to hide.”
Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E. coli, Staphylococci, Serratia
What is the most common cause of pneumoperitoneum?
Perforated Viscus -> as with Appendicitis (especially if patient has fever and abdominal pain before presenting)
What are the derivations of the developing mid/hindbrain?
- Mesencephalon -> midbrain
- Metencephalon -> Pons and Cerebellum
- Myelencephalon -> Medulla
What is the location and purpose of alpha-2 receptors in neuronal signaling?
Located on presynaptic axon -> Binds NE and by negative feedback -> inhibits further NE release into synaptic cleft
What is the purpose of Renshaw cells?
This is an interneuron in the ventral motor horn that creates a ring of inhibitor stimuli surrounding the neurons eliciting an action potential -> results in sharpening of muscle activity initiated by the motor stimulus
What nerves innervate the extraocular muscles?
LR6 SO4 3
Lateral rectus = Abducens nerve (CN VI)
Superior Oblique = Trochlear nerve (CN IV)
3 for the rest
Which organisms are prone to cause UTI?
- E. Coli (g- rods)
- Staph sapro (g+ cocci, sex active females)
- Kleb. pneumo
- Nosocomial -> Serratia (g- rod) and ENTEROCOCCUS (g+ cocci)
What is haemophilus ducreyi and what can it cause?
Gram negative rod, oxidase positive, grows on chocolate agar, beta-lactamase producing -> PAINFUL genital ulcer, with exudate and inguinal adenopathy (especially in people from developing countries)
Which bacteria require chocolate agar to grow?
HAEMOPHILUS
What is the leading cause of intraparenchymal hemorrhage and how would it appear on CT?
HYPERTENSION -> Large hyperintense focus in basal ganglia or cerebellum -> will cause deviation of intraparanchymal structures and compression of lateral ventricle (if basal ganglia)
What is hypersplenism and how may it arise?
Pancytopenia occurring in patients with enlarged spleen as would arise in a patient with alcoholic cirrhosis of the liver -> can present with signs of infection, anemia or bleeding
What lab values are seen in DIC?
- Decreased platelet count (because they are getting used up and activated)
- Increased PT and PTT (b/c coagulation factors get used up)
- Decreased Fibrinogen (linker molecule for clots, gets used up)
- Increased D-DIMER (fibrin split products - as fibrin formed from diffuse coagulation is broken down)
How does pseudogout differ from gout?
Pseudogout - basophilic, rhomboid calcium pyrophosphate crystals that are weakly bifiringent
-Usually in LARGE joints (knee)
Gout -needle shaped, negatively bifiringent yellow urate crystals
-Usually in BIG TOE (Podagra)
What is another helpful indication in a patient with respiratory depression from opioid overdose?
Pinpoint pupils and decreased gag reflex
What is Trazodone used for?
5HT2 and alpha1 receptor blocker
-Used for insomnia
SE: Sedation, PRIAPISM (trazobone), postural hypotension
What drug options are available for premature ejaculation?
- SSRIs (Paroxetine, fluoxetine, Sertraline)
- Analgesics (tramadol)
- Phosphodiesterase-5 inhibitors (Sildenafil, Vardenafil)
How does Reye syndrome arise? What are the findings?
- Viral infection treated with aspirin in a child
- Aspirin metabolites decrease beta-oxidation by reversible inhibition of MITOCHONDRIAL enzymes
- Leads to Hepatic encephalopathy, fatty liver, hypoglycemia, vomiting, hepatomegaly and coma
A keratin gel is used as a conduit filler to enhance nerve regeneration in a 4mm gap of a severed nerve. Which cells in the region would show increased mitotic activity?
Schwann cells
What characteristics of aripiprazole make it less likely for it to cause the parkinsonian symptoms of the traditional antipsychotics (neuroleptics)?
Partial agonist at Dopamine receptors
Classic drugs (Haloperidol) block dopamine D2 receptors
What are the atypical antipsychotics and their MoA?
“It’s ATYPICAL for Old CLOsets to QUIETly RISPER from A to Z” - Olanzapine, CLOzapine, QUETIapine, RISPERidone, Aripriprazole, Ziprasidone
MoA - unclear but varied effects on 5HT2, dopamine, alpha and H1 receptors (Aripiprezol is partial dop agonist, most others are blockers )
What occurs to muscle fibers during chronic peripheral neuropathy?
Remaining axons make collateral connections with denervated muscle groups -> motor units enlarge and form FIBER GROUPING -> eventually when these remaining regenerated axons die -> group atrophy
What leads to Type IV hypersensitivity reaction?
Delayed (T-cell mediated) - sensitized T cells encounter antigen then release cytokines -> leads to macrophage activation
4 Ts => T cells, Transplant Rejections, TB skin tests, Touching (contact dermatitis, like with nickel jewelry causing red scaly rash)
When is coronary artery flow at a maximum?
Early diastole
What are 4 situations that can trigger asthma attack?
Viral URIs, Allergens, Stress, methacholine challenge
What is atelectasis? And how is it usually caused?
Collapsing or closure of lungs resulting in reduced/absent gas exchange
- Usually post-op for Abd surgery (smokers and elderly)
- Poor surfactant production
How is Hydroxyurea useful in sickle cell disease?
Increases production of fetal hemoglobin F
Which testicular tumors present with increased AFP?
Non-seminoma germ cell tumors (Yolk sac, Teratoma, embryonal carcinoma if mixed)
What are the non-germ cell testicular tumors and their characteristics?
5% of all testicular tumors -> mostly benign Leydig cell (reinke crystals-gynecomastia/precocious puberty), sertoli cell, and testicular lymphoma (aggressive and from a metastatic l-oma)
What is gastroschisis?
Gastro - stomach, schisis-splitting or fissure
Anterior abd wall defect -> spilling out of abdominal contents with no overlying sac
What is the treatment for prolactinoma?
Dopamine agonists (bromocriptine or carbergoline) b/c dopamine inhibits prolactin production!
Which cells promote axonal regeneration?
Schwann Cells
