Dermal Melanocytosis — SCE Dermatology MCQ

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ModerateInflammatory DermatosesDermal MelanocytosisSCE Dermatology

A 35-year-old woman presents with acquired bilateral dermal melanocytosis affecting her malar areas. She has blue-grey pigmentation on both cheeks that has developed gradually since her 20s. What is this condition?

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Correct answer: A — Acquired bilateral naevus of Ota-like macules (Hori naevus/ABNOM)

Acquired bilateral naevus of Ota-like macules (ABNOM/Hori naevus) is a form of acquired dermal melanocytosis presenting as bilateral blue-grey or brown macules on the malar prominences, forehead, temples, and nose. It typically develops in Asian women in their 20s-30s. It is distinguished from naevus of Ota (which is usually unilateral and congenital/childhood-onset with potential scleral involvement) and from melasma (which is epidermal/mixed brown, worsened by UV/hormones). Dermoscopy of ABNOM shows homogeneous grey-blue pigmentation. Treatment is Q-switched laser (Q-switched Nd:YAG or Q-switched alexandrite), which targets deep dermal melanocytes. Multiple sessions are required.

Reference: BAD 2019; Pigmentary Disorders Review