The correct answer is D. GNAQ.

The condition shown is a Nevus of Ota.  This presents with facial dermal melanocytosis due to mosaic mutations in genes including GNAQ.

HGD (homogentisate dioxygenase) mutation is associated with alkaptonuria.  These patients can develop brown-black pigmentation of the eyes and ears (Osler sign).
HFE (homeostatic iron regulator) mutation is associated with hemochromatosis.
COL1A1 (collagen 1) mutation is associated with osteogenesis imperfecta.  These patients can have slate-grey sclerae.
POMC (proopiomelanocortin) is a precursor protein to adrenocorticotropic hormone (ACTH) and melanocytic stimulating hormone (MSH) and its expression is upregulated in Addison’s Disease.

References:

Agarwal P, Patel BC. Nevus of Ota and Ito. [Updated 2023 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK560574/

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