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Usmle > Block 17 > Flashcards

Block 17 Flashcards

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USMLE® Step 1 flashcards
1
Q

Acetylation of a drugs

A

Drugs like isoniazid, dapsone, hydralazine and procainamide, rely on acetylation.
Some people are fast acetylators and other are slow, this depends on genetic predisposition.
-slow acetylators of these drugs are at increased risk of toxic effect, while fast actylators requires larger dose to achieve theraputic effect

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2
Q

Medical conditions with polygenic inheritence

A
  1. androgentic alopecia
  2. Epilepsy
  3. Glaucoma
  4. Hypertension
  5. IHD
  6. Schizophrenia
  7. Type II D.M
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3
Q

Eggshell calcification of hilar lymph nodes (calcified node, birefringent particles surrounded by dense collagen fibers) —>

A

Silica exposure

  • can lead to fibrosis
  • symptoms usually occur after 10-20 years of exposure
  • dyspnea on excretion and productive cough.
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4
Q

Asbestosis can presnt with

A

Dyspnea on excertion, interstitial pattern of involvement in lower zones.

  • pleural plaques can be seen
  • histology shows ferruginous bodies, fusiform rods with translucent asbestos center and iron containing coating
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5
Q

L.monocytogenes meningits

A
  • resistant to third generation cephalosporins

- susceptible to ampicillin

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6
Q

Primary biliary cholangitis

A
  • autoimmune liver disease characterized by small and mid sized intrahepatic bile ducts with resulting cholestasis.
  • most common in middle aged women and associated with other autoimmune disease.
  • clinical= fatigue, itching, hepatomegaly , ALP increased , anti mitochondrial antibody.
  • biopsy shows= lymphocytic inflammation with destruction of intrahepatic bile ducts, and necrosis and micronodular regeneration of periportal tissues.
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7
Q

GVHD

A

Occurs in immuncompromised patients following transplant of allogeneic bone marrow or other lymphocyte rich tissues. Donor T-cells migrate into host tissue, where they recognize MHC as foreign.
- liver involvement is often seen with increased ALP, and lymphocytic infiltration and destruction of small intrahepatic bile ducts (similar to PBC)

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8
Q

Hypothalamus pituitary thyroid axis is regulated by

A

Negative feedback by T3 on TRH and TSH.

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9
Q

Circulating thyroid hormones exist in which forms

A
  1. T4 - major secretory product
  2. T3 -the most active form of thyroid hormone, majority arises from peripheric conversion from T4
  3. Reverse T3 (rT3)- is an inactive form that is generated almost entirely from T4
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10
Q

Selective estrogen receptor modulators

A

Drugs : tomaxifen and raloxifene
Mechanism: competitive inhibitor of E2 binding, has mixed agonist/antagonist action.
Indication: -prevention of breast cancer in high risk patients
- tomaxifen: adjuvent treatment of breast cancer
-raloxifene: postmenopausal osteoporosis.

AE: -hot flushes, venous thrombosis.
Tomaxifen AE also shows endometrial hyperplasia and carcinoma.

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11
Q

What is the most common cause of valvular aortic stenosis in developed nations

A

Calcific degeneration- progressive aortic leaflet thickening and calcification leading to restricted mobility.

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12
Q

Infective endocarditis can lead usually to

A

AR

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13
Q

Dyenein and kinesin role in virus transportation

A
  • Dynein dependent “retrograde” transport of the virus.
  • kinesin dependent “anterograde” transport of virus.
  • this is usually seen in reactivation of HSV-1 infections during times of stress or illness.
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14
Q

Pancoast tumors

A

-non small cell lung cancer arises near the superior sulcus.
- clinically determined by extent of local spread.
- compression and invasion of brachial plexus can cause ipsilateral shoulder pain, upper limb parasthesis, areflexic arm weakness.
-involvement of cervical symphatetic ganglia may lead to horners syndrome (ptosis, miosis and anhidrosis).
-

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15
Q

Lymphatic drainage of the rectum

A
  1. Lymphatics proximal to the anal line drain into the inferior mesenteric and internal illiac lymph-nodes
  2. The upper rectum and superior part of the middle rectum follows the superior rectal nodes along the superior rectal artery into the inferior mesenteric lymph nodes
  3. the middle to lower third can drain upward towards inferior mesenteric or follow middle rectal artery to the internal illiac lymph nodes.
  4. Areas distal to the anal dentate line drain primarily into the inguinal nodes, although some also can reach upper nodes.
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16
Q

Infant botulism

A
  • associated with honey intake
  • constipation usally precedes the characterstic signs of neuromuscular paralysis by a few days or weeks
  • lathergy, weakness, and reduced feeding.
  • in severe cases loss of head control and baby becomes floppy
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17
Q

What is the most common cause of death in meconium ileus disease

A

Pneumonia- usually in CF patients

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18
Q

MCC of death in CF

A

Pneumonia
Cor pulmonale
Bronchoectasis.

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19
Q

Squirt sign

A

Forceful expulsion of stools after rectal examiation in infants
Present in hirschprung disease

20
Q

ß-hemolytic gram positive bacteria, DD

A
  • s.pyogenes: PYR positive, bacteriacin sensetive,
  • S.agalactiea- PYR negative, bacteriacin resistnat, hippurate test, CAMP factor positive (L.monocytogenes also CAMP positive)
21
Q

Necrotizing fasciitis features

A

Microbiology: S.pyogenes, S.aureus. C.perferingen, polymicrobial
Pathogenesis: bacteria spread rapidly through subcutaneous tissues and deep fascia, undermining the skin, usually involves extremities and perineal region.
clinical:history of minor trauma, erythema of overlying skin, swelling and edema, pain out of proportion to examination findings, systemic symptoms.
Treatment: requires surgical debridemant and broad spectrum antibiotics

22
Q

Acute hepatitis B

A
  • systemic, skin and joint symptoms.
  • hepatomegaly
  • elevated transaminases.
  • incubation period is 30-180 days
  • sexually, parenterally and vertical transmission.
  • pts may develop serum sickness like syndrome with joint pain, lymphadenopathy and pruritic urticarial vasculitis rash.
  • most patients have non-ecteric hepatitis
23
Q

Acute hepatitis C

A

Typically assmymptomatic, dermatologic manifestations are seen in chronic infections.
-sexual transmission is very rare, usually parenteral transmission.

24
Q

Headaches, along with flat,pigmented,spots on the trunk. Also multiple subcentimter, soft ,fleshy cutaneous tumors on the trunk and neck.

A

NF-1

  • AD, caused by mutation in NF1 tumor supressor gene. Patient develops hyper pigmented macules (over the turnk) soon after birth and are at increased risk for developing CNS neoplasms (eg. Optic gliomas, pilocytic astrocytoma) which can cause elevation of ICP and headache.
  • cutaneous neurofibromas usually composed of schwann cell( which derived from neural crest cells).
25
Q

Kehr sign

A

Shoulder pain represents referred pain due to peritoneal irritation.

26
Q

Aminoglycoside resistnace

A

Develops through bacterial production of aminoglycosides modifying enzymes that transfers different chemical groups to aminoglycosides antibiotic molecule outside of the bacterium, thereby decreasing the ability of antibiotic to bind to ribosomes and exert is antimicrobial effects. (Mediated by plasmid or transposons)

27
Q

Vancomycin reistance in enterococci

A

VanA ligase replaces D-alanyl D-alanine to D-alanyl D-lactate, thereby preventing vancomycin binding.

28
Q

Tetracycline resistance

A

Can occur through a decrease in intracellular concentration of the drug and via synthesis fo a protein that allows ribosome to perform translation even in the presence of antibiotics

29
Q

Zellweger syndrome

A

Defective peroxisomal biogenesis.
It typically presents in early infancy with carniofacial abnormalities (widened sutures, large anterior fontanelle), hepatomegaly, and profound neurologic defects (hypotonia, seizures, developmental delay).
Death usually occuurs within months.

30
Q

X-linked adrenoleukodystrophy

A

-defective transport of VLCFA into prexisisomes. Patients present in childhood or adulthood with neurologic deterioration and adrenal insufficiency as VLCFA accumulate in CNS and adrenal gland

31
Q

The 50% infectios dose (ID50) corresponds to

A

Minimum number of organism required to cause a disease in 50% of affected individuals.

32
Q

CD55 absence indicates

A

Paroxysmal nocturnal hemoglobinuria

33
Q

Paroxysmal nocturnal hemoglobinuria would show which renal changes

A

-hemosiderosis, due to increased destruction of RBC—> iron overload —> iron deposition in the kidney —> PCT dysfunction with interstitial scarring and cortical infarcts.

34
Q

Cast nephropathy usually seen in

A

-multiple myeloma,

35
Q

Cholestasis clinical

A

Fatigue ,pruritus, hepatomegaly and elevated ALP.
Cholestatasis arises secondary to hepatocellular dysfunction, or intrahepatic or extrahepatic dysfunction.
-both obstructive and non obstructive cholestasis are charactrized by deposition of bile pigment within the hepatic parenchyma, often with green brown plugs in the dilated bile canaliculi.
- the reduction in bile flow causes intestinal malabsorption of fats and fat soulble vitamins. (ADEK)

36
Q

In atherosclerosis of coronary artery, which is responsible for making the fibrous cap (synthesis)

A

Smooth muscle cells

37
Q

Sturge weber syndrome

A

Rare congenital neucutaneous disorder charactrized by the presence of cutaneous facial angiomas as well as leptomeningeal angioma.
The condition is associated with mental retardation, seizures, hemiplegia, and skull radiopacities. (Tram track calcification)

38
Q

Oseler weber rendu syndrome

A
  • AD,congenital telengectasia to the skin, and mucus membrane.
  • rupture of telengectasia may lead epistaxis, gi bleeding and hematuria.
39
Q

AV shunts after injury

A

Reult from the formation of AV fistulas. An AV fistula is an abnormal communication between an artery and vein that bypasses the arterioles, the major source of resistance in the vascular system.
- thus AV sunts allow blood under arterial pressure to directly enter the venous system —>increases cardiac preload —>increasing the rate and volume of blood flow back to the heart.—> TPR decreased —>decrease in afterload

40
Q

Pulsatile mass with a thrill on palpation and presence of constant bruit over the site.

A

AV shunt

41
Q

Treatment of narcolepsy

A

Modafinil, non-amphetamine simulant is the first line, well tolerated and drug abuse is rare.

42
Q

Causes of gynecomastia

A
  1. Increased E2 = -testicular cancer, obesity, cirhosis, thyrotoxicosis or androgen use
  2. Androgen deficiency= hyperprolactinemia, renal failure, and primary or seconday male hypogonadism.
  3. Medication effect=
    A. Decreased androgen production (GnRH agonist, ketoconazole)
    B. Decreased peripheral conversion to DHT(finasteride)
    C. Inhibition of androgen receptor ( spironolactone, bicaultamide)
43
Q

Gynecomastia prevention in males can be done using

A

Tomaxifen

44
Q

Uncontorlled diabetes can cause CN III ?

A

-it can cause diabetic CN III mononueropathy which classicaly present as acute onset diplopia
- ptosis may occur
-its caused by ischemic nerve damage which predominantly involves the core of the CNIII with relative sparing of the peripheral part.
The somatic component of CN III that innervates the extra ocular muscles is located centrally,but autonomic component responsible for pupillary constriction and accomodation is located in the peripheral aspect of the nerve, therefore pupillary size and reactivity is normal.

45
Q

Loop of henle water permability

A

The descending loop is permeable to water while the ascending thick and thin are impermeable to water. (In the ascending limb the osmolarity decreases due to passive absorption of NaCl in the skin region as well as active transport of electrolytes out of the lumen by Na/k/2Cl- cotransporter in the thick portion.

Usmle (45 decks)

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