Synopsis
Distinguish fungal nail disease from common dystrophic mimics, collect representative keratin before systemic treatment, and prescribe topical or oral antifungal therapy with liver and interaction safeguards.
- Onychomycosis commonly produces distal or lateral yellow-white discolouration, subungual debris, thickening, brittleness and onycholysis, but psoriasis and trauma can look identical.
- Examine every nail plus toe webs, soles, palms and scalp; untreated tinea pedis can repeatedly reseed a treated toenail.
- Before oral therapy, clean away surface contaminants, clip back to the most proximal diseased nail possible and include subungual debris for microscopy and culture or the local validated molecular pathway.
Key red flags
A new irregular pigmented nail band, periungual pigment, ulceration, bleeding or a nail-bed mass requires urgent melanoma assessment; painful spreading erythema, diabetic foot ulceration, ischaemia or systemic infection needs prompt acute foot or infection care.
A new irregular longitudinal band, Hutchinson pigment, nail destruction, bleeding or a mass is not assumed fungal and needs urgent lesion assessment.
Investigation priorities
Obtain active infected keratin for laboratory confirmation before systemic treatment.
Management branches
Nail dystrophy is uncertain or oral antifungal treatment is being considered.
- Stop cosmetic polish, clean the plate and examine all nails, skin and feet for psoriasis, trauma, tinea and a suspicious pigmented or destructive lesion.
- Clip the most proximal accessible diseased plate and collect generous subungual material, sending the exact site and treatment history for microscopy and culture or local PCR.