A 28-year-old man has onychomycosis in which the infection begins at the proximal nail fold and extends distally as a white patch under the nail plate. There is no history of trauma, tinea pedis, or nail surgery. Which pattern of onychomycosis is this, and why does it raise concern?

• A Distal lateral subungual type, commonest pattern worldwide
• B White superficial type, caused by direct invasion of the dorsal nail plate
• C Endonyx type, caused by endothrix invasion without nail bed involvement
• D Proximal subungual type, an uncommon marker of immunosuppression such as HIV ✓

Explanation

Proximal subungual onychomycosis arises when organisms invade via the proximal nail fold and is distinctly uncommon in immunocompetent people. Its appearance in a young adult without local predisposing factors should prompt testing for HIV and assessment of immune status. Distal lateral subungual onychomycosis is the commonest pattern and is usually associated with tinea pedis and trauma, while white superficial type invades the dorsal plate surface.

Reference: Fitzpatrick's Dermatology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.