UWorld-Dermatology

Question 1

what kind of hypersensitivity (and what cells) is tested for with the Candida antigen skin test

Answer 1

type 4 (T-cell-mediated hypersensitivity)

the active cells of cell-mediated immunity are macrophages, CD 4+ T cells, CD 8+ T cells and NK cells

Question 2

what is the different between the symptoms of acute intermittent porphyria and porphyria cutanea tarda?
what about the causal enzyme defects?

Answer 2

acute intermittent porphyria: abd. pain, port-wine urine, psychological disturbances and polyneuropathy, precipitated by drugs, alcohol and starvation; deficient uroporphyrinogen I synthase/ porphobilinogen deaminase

porphyria cutanea tarda: blistering photosensitivity;
deficient uroporphyrinogen decarboxylase

Question 3

RNA that have a high percentage of modified bases like dihydrouracil, pseudouracil, thymidine, and acetylcytosine has what at its 3’ end

Answer 3

t-RNA have modified bases and at the 3’ end there is a CCA sequence (“can carry aminoacids”)

Question 4

what is found in the T arm of tRNA and what is the T arm responsible for doing

Answer 4

T arm has TpsiC sequence (thymidine, pseudouracil and cytosine); it is responsible for binding the ribosome

Question 5

what is the D arm of tRNA responsible for doing

Answer 5

D arm has dihydrouracil residues and is responsible for binding by the correct aminoacyl-tRNA synthase

Question 6

lentigo vs. ephelis (freckle)

Answer 6

lentigo is a pigmented macule that has increased melanocytes that proliferate in a horizontal manner

ephelis is a pigmented macule with increased melanin production, but normal number of melanocytes

Question 7

lentigo vs. pigmented nevus (mole)

Answer 7

lentigo is flattened because the hyperproliferation of melanocytes is horizontal and confined to the basal layer

nevus is raised because the melanocytes hyperproliferate upward

Question 8

Hartnup disease vs. Fanconi syndrome

Answer 8

Hartnup is inability to reabsorb neutral amino acids (i.e. tryptophan, Phe, Ala, Val, Ile, Leu); charged amino acids like arginine and proline are still reabsorbed while in Fanconi syndrome (generalized aminoaciduria) they are not

Question 9

what occurrence in invasive breast cancer causes inversion of the nipple or retractions of the skin?
what about peau d’ orange?

Answer 9

invasion of the suspensory Cooper’s ligaments leads to nipple inversion or retractions of the skin

blockage of lymphatic drainage causes peau d’ orange

Question 10

for chlorhexidine, alcohol, H2O2, and Iodine list which are sporicidal and how they work

Answer 10

chlorhexidine: destroys cell membranes, coagulates cytoplasm (non-sporicidal)
alcohol: destroys cell membranes, denatures proteins (non-sporicidal)
hydrogen peroxide uses free radicals and is sporicidal
idione halogenates proteins and nucleic acids and is sporicidal

Question 11

what is seen on light microscopy in shingles (VZV)

Answer 11

intranuclear inclusions in keratinocytes and large multinucleated cells

Question 12

excessive wound contraction due to excessive matrix metalloproteases and myofibroblasts may lead to what skin abnormality

Answer 12

wound contracture

Question 13

if Gibbs free energy for a reaction is positive, will the Keq be greater than one or less than one

Answer 13

less than one (less products than reactants)