Clinical features

The appearance of infected nails will vary according to the infecting organism. Particular note should be made of the extent of any infection, whether it affects adjacent skin and the number of nails infected. Evidence of previous trauma or damage to the affected nails should be sought.

As the disease progresses the nail unit appears thick, brittle and discoloured, often with a yellow hue. There may be associated onycholysis and paronychial inflammation (1). Onychomycosis can be classified clinically into:

Distal and lateral subungual onychomycosis (DLSO)

• most common type
• frequently caused by dermatophyte organisms, candida species and molds may also be responsible
• initially affects the distal or lateral portion of the nail which spreads proximally causing subungual hyperkeratosis and onycholysis (1)
• involvement of the nail plate is not seen initially but it may become friable and may break as the disease progresses
• associated tinea pedis can be seen in most of the patients (2)

Superficial white onychomycosis (SWO)

• almost always caused by dermatophyte infections
• involvement of the nail plate is seen rather than the nail bed (2)
• small well demarcated superficial white patches can be seen which may coalesce and cover the whole nail (1)
• nail plates are brittle and may crumble (1)

Proximal subungual onychomycosis (PSO)

• a rare type
• often seen in AIDS and immunosuppressed patients
• infection begins in the proximal nail fold, reaches the nail matrix and then the deep surface of the nail plate (1).

Total dystrophic onychomycosis

• most severe form of the disease
• entire nail plate is completely destroyed revealing an abnormally thickened nail bed (1)
• any one of the above clinical forms may in time develop in to total nail dystrophy (2)

Reference:

• (1) Winston JA, Miller JL. Treatment of onychomycosis in diabetic patients. Clinical Diabetes2006;24(4):160-166
• (2) Roberts DT, Taylor WD, Boyle J. Guidelines for treatment of onychomycosis. British Journal of Dermatology 2003;148:402–410