ABD Pigmentary Disorders 2

Question 1

Generalized hyperpigmentation in Addison's disease (primary adrenal insufficiency) is caused by:

Accepted Answer

Excess ACTH cross-reacting with MC1R on melanocytes due to loss of cortisol feedback

Answer

Loss of cortisol removes negative feedback on the pituitary, causing excess POMC cleavage into ACTH and alpha-MSH; ACTH cross-reacts with the melanocortin-1 receptor (MC1R) on melanocytes, increasing melanin production.

Question 2

Long-term amiodarone therapy produces a distinctive skin discoloration described as:

Accepted Answer

Slate-gray to blue-gray from drug-lipofuscin complexes in dermal macrophages in sun-exposed areas

Answer

Amiodarone's iodine content renders it phototoxic; chronic exposure causes iodine-containing drug-lipofuscin complexes to accumulate in dermal macrophages, producing a characteristic slate-gray or blue-gray pigmentation in photoexposed skin.

Question 3

Which combination of features best differentiates dermal melanocytosis (Mongolian spot) from non-accidental trauma (bruising) in an infant?

Accepted Answer

All of the above

Answer

Mongolian spots are congenital (present at birth), located characteristically on the lumbosacral region, and show stable blue-gray color without the sequential color change (purple→green→yellow) or swelling that accompanies bruising.

Question 4

A halo nevus with a depigmented ring surrounding a central benign-appearing melanocytic nevus is best explained by:

Accepted Answer

Cytotoxic T-lymphocyte-mediated immune destruction of nevus melanocytes extending to surrounding normal melanocytes

Answer

Halo nevi result from a cytotoxic CD8+ T-cell immune response targeting nevus melanocytes that extends to adjacent normal melanocytes, producing a depigmented halo — a mechanism shared with vitiligo.

Question 5

Progressive macular hypomelanosis is distinguished from pityriasis versicolor by which Wood's lamp finding?

Accepted Answer

Folliculocentric red fluorescence in coalescing hypopigmented trunk macules

Answer

Progressive macular hypomelanosis shows pathognomonic folliculocentric red fluorescence under Wood's lamp, caused by porphyrins produced by Cutibacterium acnes colonizing follicles, unlike pityriasis versicolor's yellow-green fluorescence.

American Board of Dermatology (ABD) Practice Test

American Board of Dermatology (ABD) Practice Test

ABD Pigmentary Disorders 2