ABD Pigmentary Disorders 1 — Questions and Answers
Question 1: Which autoantigen is most commonly targeted by autoantibodies in generalized vitiligo?
- Tyrosinase and tyrosinase-related proteins (TRP-1, TRP-2) (Correct answer)
- Desmoglein 3
- BP180 (type XVII collagen)
- Antinuclear antigens (ANA)
Correct answer: Tyrosinase and tyrosinase-related proteins (TRP-1, TRP-2)
Vitiligo involves autoimmune destruction of melanocytes, with autoantibodies most commonly targeting tyrosinase and tyrosinase-related proteins TRP-1 and TRP-2.
Question 2: Under Wood's lamp examination, vitiligo-affected skin characteristically shows:
- Yellow-green fluorescence
- Bright blue-white (chalk-white) fluorescence accentuating depigmentation (Correct answer)
- Coral-pink fluorescence
- Orange-red folliculocentric fluorescence
Correct answer: Bright blue-white (chalk-white) fluorescence accentuating depigmentation
Vitiligo shows striking bright blue-white fluorescence under Wood's lamp due to complete melanin loss, which accentuates the depigmented patches and helps reveal subclinical lesions.
Question 3: Kligman's formula, the gold standard for melasma treatment, consists of which combination?
- Tretinoin + hydroquinone + low-potency topical corticosteroid (Correct answer)
- Azelaic acid + kojic acid + benzoyl peroxide
- Salicylic acid + niacinamide + retinol
- Glycolic acid + vitamin C + broad-spectrum sunscreen alone
Correct answer: Tretinoin + hydroquinone + low-potency topical corticosteroid
Kligman's formula combines tretinoin (enhances penetration and turnover), hydroquinone (inhibits tyrosinase), and a low-potency corticosteroid (reduces irritation), targeting melasma through multiple mechanisms.
Question 4: Post-inflammatory hyperpigmentation (PIH) is more persistent in darker skin types primarily because:
- Melanocytes are more numerous in darker skin
- Both epidermal melanin deposition and dermal melanophage formation occur (Correct answer)
- Keratinocyte turnover is slower
- Mast cell density is higher in darker skin
Correct answer: Both epidermal melanin deposition and dermal melanophage formation occur
PIH involves both epidermal hyperpigmentation from activated melanocytes and dermal melanophages from melanin incontinence; the dermal component is difficult to treat and accounts for prolonged PIH in darker phototypes.
Question 5: Oculocutaneous albinism type 1A (OCA1A) results from mutations in which gene, producing what enzymatic defect?
- OCA2 gene; defective P-protein melanosomal transporter
- TYR gene; complete absence of tyrosinase enzyme activity (Correct answer)
- TYRP1 gene; defective tyrosinase-related protein 1
- MC1R gene; defective melanocortin-1 receptor signaling
Correct answer: TYR gene; complete absence of tyrosinase enzyme activity
OCA1A is caused by loss-of-function mutations in the TYR gene encoding tyrosinase, the rate-limiting enzyme in melanin biosynthesis, resulting in complete absence of melanin production.
Question 6: Nevus of Ota (oculodermal melanocytosis) is classically distributed along which anatomical territory?
- Bilateral periorbital and malar regions symmetrically
- Unilateral distribution along the ophthalmic and maxillary divisions of the trigeminal nerve (Correct answer)
- Diffuse facial involvement with ipsilateral scalp extension
- Bilateral malar distribution sparing periorbital skin
Correct answer: Unilateral distribution along the ophthalmic and maxillary divisions of the trigeminal nerve
Nevus of Ota presents as unilateral bluish-gray dermal melanocytosis in the distribution of the first (ophthalmic, V1) and second (maxillary, V2) divisions of the trigeminal nerve, often involving the ipsilateral sclera.
Question 7: Which feature best distinguishes pityriasis alba from vitiligo in a child with facial hypopigmented patches?
- Lesions appearing on the face
- Incomplete hypopigmentation with fine scale and association with atopic dermatitis (Correct answer)
- Response to topical calcineurin inhibitors
- Worsening with ultraviolet light exposure
Correct answer: Incomplete hypopigmentation with fine scale and association with atopic dermatitis
Pityriasis alba shows incomplete hypopigmentation (not total depigmentation), has subtle fine scale, and occurs in the context of atopic dermatitis, whereas vitiligo shows complete melanin loss without scale.
ABD Pigmentary Disorders 1
Which autoantigen is most commonly targeted by autoantibodies in generalized vitiligo?