A 48-year-old man has a longitudinal dark band on the right great toenail widening over two years. Pigmentation extends onto the proximal nail fold and hyponychium. Biopsy of the nail matrix confirms melanoma. The extension of pigment onto the nail folds is called:

• A Koebner phenomenon
• B Auspitz sign
• C Darier sign
• D Hutchinson sign ✓

Explanation

Hutchinson sign is periungual extension of pigment onto the proximal nail fold or hyponychium and strongly suggests subungual melanoma rather than benign longitudinal melanonychia. Auspitz sign refers to pinpoint bleeding after scale removal in psoriasis, Darier sign to urtication of a mastocytoma, and Koebner phenomenon to lesion induction by trauma, so none fit this finding.

Reference: Bolognia Dermatology, 5th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.