Pigmentary Disorders Flashcards

Incontinentia pigmenti (Bloch-Sulzberger syndrome) progresses through four cutaneous stages in which order?

Answer: Vesicles/bullae → verrucous → whorled hyperpigmentation (Blaschko's lines) → hypopigmented/atrophic

Incontinentia pigmenti classically follows four sequential stages: Stage 1 (vesicular/bullous, eosinophilic), Stage 2 (verrucous), Stage 3 (whorled hyperpigmentation along Blaschko's lines from melanin incontinence), and Stage 4 (hypopigmented/atrophic).

Which constellation of findings is diagnostic of Waardenburg syndrome?

Answer: Sensorineural deafness, white forelock, heterochromia iridis, and dystopia canthorum

Waardenburg syndrome is characterized by sensorineural deafness, white forelock (poliosis), heterochromia iridis, and dystopia canthorum (lateral displacement of inner canthi), caused by mutations in PAX3, MITF, SOX10, EDN3, or EDNRB affecting neural crest melanocyte migration.

In a fair-skinned infant suspected of having tuberous sclerosis complex, ash-leaf macules are best detected using:

Answer: Wood's lamp examination in a darkened room

Wood's lamp examination in a darkened room accentuates the hypopigmented ash-leaf macules by creating high contrast, making subclinical lesions visible even in fair-skinned infants who may otherwise appear unaffected.

Erythema dyschromicum perstans (ashy dermatosis) is best characterized by which description?

Answer: Gray-brown ('ashy') macules and patches with active erythematous borders in early stages, predominantly affecting individuals with darker phototypes

Erythema dyschromicum perstans presents as gray-brown ('ashy') hyperpigmented macules and patches with erythematous borders in early active disease, predominantly affecting Hispanic and darker-skinned individuals, and is considered a form of interface dermatitis.

Perioral and acral mucocutaneous lentigines in Peutz-Jeghers syndrome result from germline mutations in which gene?

Answer: STK11/LKB1 (serine-threonine kinase 11) on chromosome 19p

Peutz-Jeghers syndrome is caused by autosomal dominant germline mutations in STK11 (LKB1), encoding a serine-threonine kinase tumor suppressor on chromosome 19p13, leading to mucocutaneous lentigines and hamartomatous gastrointestinal polyps.

Dyschromatosis symmetrica hereditaria, featuring a mixture of hyper- and hypopigmented macules on the dorsal hands and feet, is most commonly caused by autosomal dominant mutations in:

Answer: ADAR1 (adenosine deaminase acting on RNA)

Dyschromatosis symmetrica hereditaria is caused by autosomal dominant mutations in ADAR1, which encodes adenosine deaminase acting on RNA (an RNA editing enzyme), and is not caused by mutations in classical melanogenesis pathway genes.

Becker's nevus (Becker's melanosis) is best classified as:

Answer: An organoid hamartoma with androgen-sensitive smooth muscle, presenting as hyperpigmented hypertrichotic patch on the shoulder of adolescent males

Becker's nevus is a hamartoma containing androgen-responsive arrector pili smooth muscle, which accounts for the hypertrichosis; it typically appears on the shoulder/upper trunk of adolescent males and carries no significant malignant potential.