Onychomycosis

What it is

Onychomycosis is fungal infection of the nails. Three groups of organisms cause it:

• Dermatophytes, mainly Trichophyton rubrum, which accounts for 90% of cases
• Yeasts, such as Candida
• Non-dermatophyte moulds

Which of the three is responsible matters, because the dermatophyte and the Candida nail are treated differently.

How it presents

Unsightly nails are a common reason for presentation. Thickened, rough, opaque nails are the most common finding.

How it is diagnosed

Take nail clippings and scrapings of the affected nail. Diagnosis should be confirmed by microbiology before starting treatment, and the oral regimen is written for disease confirmed on fungal culture as dermatophyte.

The tests named for it are the KOH prep, fungal culture and the PAS stain, and the KOH prep shows hyphae, so there is no need to biopsy. Who should be investigated is a short list: diabetics, immunosuppressed patients, multiple or refractory nail involvement, and when the diagnosis is uncertain. The case this is written around is a diabetic patient who presented with a nail change, which is why the diabetic sits first on that list.