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USMLE Step 1 > Biochem - Stuff Missed > Flashcards

Biochem - Stuff Missed Flashcards

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USMLE® Step 1 flashcards
1
Q

Hartnup disease

A

results from niacin deficiency
- niacin deficiency may be due to loss of dietary tryptophan, resulting from defective intestinal and renal tubular absorption of amino acid

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2
Q

Niacin/Vitamin B3

A

synthesized from tryptophan

- tryptophan is an essential amino acid

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3
Q

Signs of Riboflavin deficiency

A 
Chelosis  Glossitis
Keratitis, Conjunctivitis, 
Photophophoia
Lacrimation
Marked Corneal vascularization
Seborrheic dermatitis
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4
Q

Vitamin E

A
  • aka tocopherol

- functions as scavenger of free radicals (antioxidant)

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5
Q

Signs of Vitamin E deficiency

A

myelopathy

neurologic dysfunction

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6
Q

Vitamin B2 (Riboflavin)

A
  • form FMN and FAD to form enzymes for electron transport
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7
Q

Pyroxidine (Vitamin B2)

A

coenzyme for decarboxylation and transamination of amino acids

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8
Q

Deficiency of Pyroxidine

A

Anemia
Peripheral neuropathy
Dermatitis

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9
Q

Phenylketonuria

A

inborn deficiency of phenylalanine hydroxylase to metabolize phenylalanine.

  • manifests developmental delay, mental retardation, mousy body odor, and fair skin coloring
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10
Q

Niemann-Pick disease

A
  • AR
  • deficiency in sphingomyelinase
  • progressive neurodegenerative disease
  • hepatosplenomegaly
  • cherry red macula
  • foamy macrophages filled with spingomyelin
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11
Q

Fabry’s disease

A
  • X-linked disease
  • deficency in alpha-galactosidase A
  • peripheral neuropathy of hands/feet
  • angiokeratomas
  • CV/renal disease
  • accumulation of ceramide trihexosidase
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12
Q

Gaucher’s disease-

A
  • Autosomal recessive
  • deficiency in GLUCOcerebrocisidase
  • very common
  • hepatosplenomegaly
  • asceptic necrosis of femur
  • Bone crises
  • Gaucher cells (macrophages that look like crumpled tissue paper)
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13
Q

Tay-Sachs disease

A
  • Autosomal recessive
  • deficient in Hexosaminidase A
  • accumulation of GM2 ganglioside
  • progressive neurodegeneration
  • developmental delay
  • cherry red spot of macula
  • lysosomes with onion skin
  • NO HEPATOSPLENOMEGALY (vs. Niemann-Picks disease)
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14
Q

Krabbe’s disease

A
  • AR
  • deficient in GALACTOcerebrocidase, leading to accumulation of galactocerebroside
  • leads to peripheral neuropathy
  • developmental delay
  • optic atrophy
  • globoid cells
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15
Q

Metachromatic leukodystrophy

A
  • AR
  • deficient in arylsulfatase A
  • accumulation of Cerebroside sulfate
  • central and peripheral demyelination with ataxia
  • Dementia
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16
Q

Hurler’s syndrome

A
  • deficient in alpha-L-iduronidase
  • accumulation of heparan sulfat, dermatan sulfate
  • presents with developmental delay,
  • gargoylism (abnormal facial features)
  • corneal clouding
  • hepatosplenomegaly
17
Q

Hunter’s syndrome

A
  • deficient in Iduronate sulfatase
  • Mild Hurler’s sndrome (no corneal clouding)
  • ## mild developmental delay
18
Q

Acyclovir

A
  • monophosphorylation of viral thymidine kinase is the first step in the active conversion of acyclovir to active stae
  • more effective against HSV and VZV than CMV or EBV
19
Q

Pituitary adenomas

A
  • causs symptoms from mass effect
  • produce endocrine disorders
  • prolactinomas are most common
  • excess prolactin causes amenorrhea and galactorrhea
  • bitemporal heminopsia from compression of optic chiasm is common
20
Q

Interferons

A
  • produced by eukaryotic cells in response to viral infection
  • act as cytokins on neighboring cells, to stimulate neighbors to produce antivural proteins that impair viral synthesis
21
Q

Edwards Syndrome

A
  • Trisomy 18
  • presents as micrognathia, low set ears, rockerbottom feet
  • clenched hands with index finger overring the middle finger and fifth finger overriding fourth finger
22
Q

Patau Syndrome

A
  • Trisomy 13
  • presents as holoproscephapy
  • microcepthaly
  • polydactly and rocker bottom feet
  • multiple facial abnormalities including cleft lip/cleft palat
23
Q

Most common cause of pneumonia, otitis media, and meningitis in adults

A

S. pneumoniae

- appears as Gram positive lancet shaped cocci in pairs

24
Q

Most common cause of bacteria in adults of all ages

A

S. peneuomoniae

25
Q

Fragile X Syndrome

A
  • defect in FMR1 gene on long arm of chromosome Z
  • increased number of CGG trinucleotide repeats leads to hypermethylation of cytosine bases and gene activation
  • leads to mental retardation, facial dysmorphism, macro orchidism
26
Q

Chromosomal instability disorders

A
  • Xeroderma pigmentosum
  • Ataxia-telegientascia
  • Fanconi’s anemia
  • Bloom syndrome
27
Q

Lynch syndrome

A

associated with defect in DNA mismatch repair genes

- increased risk of hereditary non-polyposis cancer (HNPCC) and extraintestinal malignancies

28
Q

Homocystinuria Findings

A
  • Increased levels of homocysteine in urine
  • Mental retardation
  • Osteoporosis
  • Tall stature
  • Kyphosis
  • Lens subluxation (downward and inward)
  • Atherosclerosis (stroke and MI)
29
Q

Homocystinuria

A
  • autosomal recessive - comes in 3 forms:
  • can result from cystathionine deficiency (tx with less MEt and increased methionine, B12 , and folate in diet)
  • decreased affinity for cystathionine synthase for pyroxidase (increased B6)
  • Homocysteine methyltransferase deficiency (*requires B12)
30
Q

Maple syrup urine disease

A
  • autosomal recessive
  • blocked degradation of branched amino acids (Isoleucine, Leucine, Valine)
  • alpha ketoacid dehydrogenase (b1)
  • caused increased of serum alpha-ketoacids
  • can cause severe CNS defects, mental retardation, and death
  • urine smells like maple syrup
31
Q

Hartnup disease

A
  • autosomal recessive disorder
  • defective neutral amino acid transporter on renal and intestinal epithelial cells
  • causes tryptophan excretion in in urine and decreased absorption in gut
  • can lead to pellagra
  • associated with B6 deficiency
32
Q

Alkaptonuria

A

congenital deficiency of homofentisic acid in degradative pathway of tyrosine to fumate

  • autosomal recessive and benign
  • Dark connective tissue, Brown pigmented sclera, black urine upon exposure to ait
  • may have debilitating arthralgia ( Homocysteine not good for cartilage)
33
Q

Listeria

A
  • transmitted through contaminated food
  • causes sepsis and meningitis in immunocompromised adults
  • common cause of infantile meningitis
  • grows well in cold temps
  • gram positive but tumbling motility key feature
34
Q

Aspergillosis

A
  • neutropenic patients are at risk for Aspergillus fumigatus
  • produces septate hypate with ACUTE V-shaped branching
  • causes invasive aspergillosis (seen in immunosuppressed patients)
  • aspergillomas (seen in TB, emphysema and sarcoid pts)
  • allergic pulmonary aspergillosus (seen in asthma patients)

USMLE Step 1 (34 decks)

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