Dermatology

Question 1

Initial infection causing hidradenitis suppurativa is what? With time, what other organism may predominate?

Answer 1

S aureus intially

Proteus later

Question 2

What finding would support a diagnosis of keratoacanthoma over SCC?

Answer 2

Central crater in keratocacanthomas.

Question 3

Localized or generalized hair loss, probably related to autoimmune attack on hair follicles is what?

Answer 3

Alopecia areata
Exclamation point hairs are pathognomonic
Evidence of autoimmune process: antithyroglobulin, antimicrosomal ab

Question 4

Autoantibodies to what proteins cause bullous pemphigoid? Sx?

Answer 4

Integrins of hemidesmosomes (binds basement membrane)

Tense bullae that remain intact. Do NOT usually affect mucosa

Question 5

Autoantiboides to what proteins cause pemphigus vulgaris?

Answer 5

Cadherins (desmogleins) of desmosomes (bind keratinocytes)
Positive Nikolsky sign - blister with gentle traction
Can involve mucosa!

Question 6

AK lead to what skin cancer?

Answer 6

Squamous cell carcinoma

Question 7

Young athlete with comedonal and inflammatory nodular eruption on patient’s face, chest and back. Cause of rash?

Answer 7

Methyltestosterone

Androgens promote follicular epidermal hyperproliferation and excess sebum production

Question 8

Red-Blue tumor under the nail = glomangioma (benign glomus tumor). What cell type does it originate from?

Answer 8

Smooth mm cells - control THERMOREGULATORY functions of dermal glomus bodies

Question 9

Xanthelasmas may occur in association with what?

Answer 9

Primary or secondary hyperlipidemia
Cholestatic conditions like primary biliary cirrhosis are a potential cause of hypercholesterolemia leading to xanthelasma

Question 10

What causes wrinkling?

Answer 10

1. epidermal atrophy with flattening of rete ridges
2. Dec collagen fibril production
3. Inc degradation of collagen and elastin in the dermis
4. Inc crosslinking of collagen

Question 11

Autoimmune disorder characterized by inflammatory myopathy (proximal mm weakness), gottron papules (flat-topped papules over joints), and heliotrope rash

Answer 11

Dermatomyositis

Question 12

A defect in what enzyme is the cause of xeroderma pigmentosum?

Answer 12

Endonuclease - nucleotide excision repair defect

Excises distortions in DNA caused by thymine dimers

Question 13

Erythematous pruritic papules, vesicles and bullae that appear bilaterally and symmetrically on the extensor surfaces is strongly assoc with what GI disease?

Answer 13

Celiac disease - dermatitis herpetiformis

Question 14

Differentiate junctional, compound, and intradermal nevus

Answer 14

Junctional - nevus cells limited to dermoepidermal junction
Compound - both dermal and epidermal involvement
Intradermal - “older lesions” - nevus cells in dermal layer

Question 15

Vitiligo is a common condition characterized by patches of hypopigmented areas of the skin and is caused by what?

Answer 15

Loss/absence of epidermal melanocytes in the skin

Note: Albinism is caused by absent or defective tyrosinase that results in lack of melanin. Melanocytes are present.
Post inflam hypopigmentation occurs by redistribution of existing melanin in the skin or reduced transfer of melanin to keratinocytes

Question 16

Maculopapular rash, diffuse itching after showers, dizzy, syncope, flushing, abdominal cramps. Skin biopsy showing large cluster of mast cells that are positive for KIT (CD117) is what condition?

Answer 16

Systemic mastocytosis- abnormal prolif of mast cells and inc histamine release –> hypersecretion of GASTRIC ACID by parietal cells in the stomach

Question 17

Patient with light skin and silvery hair with history of recurrent skin and respiratory infections and horizontal nystagmus has what condition?

Answer 17

Chediak-Higashi syndrome
defect in neutrophil phagosome lysosome fusion –> abnormal giant lysosomal inclusions visible on light microscopy
Partial oculocutaneous albinism is d/t abnormal melanin storage in melanocytes

Question 18

Effect of Tretinoin on Collagen Formation in Photodamaged Skin

Answer 18

Activation of nuclear gene transcription
Tretinoin is a hormone. These nuclear receptors are related to a super family of nuclear DNA transcription factors, which include STEROID, THYROID hormone, and vitamin D receptors. The nuclear retinoic acid receptor family called RARs

Question 19

hemangiomas are derived from what tissue?

Answer 19

Endothelial cell type -  mesenchyme-
Blood vessels (endothelium) can turn into benign hemangioma