Importance: 

Tinea Unguium (Onychomycosis) is most often caused by Trichophyton rubrum and T. interdigitale. It should be distinguished from other causes of onychomycosis:

Candida species, which often cause paronychia, infection of skin around the nail. 

Clinical features:

Tinea unguium is increasingly prevalent with increased age and spreads from tinea pedis or less often, tinea manuum. It may affect one or more toenails and/or fingernails and most often involves the great toenail or the little toenail. It can present as several different patterns:

• Lateral onychomycosis. A yellow or white opaque streak appears at one side of the nail.
• Subungual hyperkeratosis. Scaling occurs under the nail.
• Distal onycholysis. The end of the nail lifts up. The free edge often crumbles.
• Superficial white-yellow  onychomycosis. Flaky white patches and pits appear on the top of the nail plate.

• Proximal onychomycosis. Yellow spots appear in the half-moon (lunula).
• Complete destruction of the nail.
• Pinched nail, excessive transverse curvature, progressively pinching the nail bed distally, resulting in cosmetic discomfort, pain and functional limitation.

Investigation:

Nail clippings for fungus microscopic examination. 

Fungus culture can be done where laboratory facilities are available.

Treatment of Tinea Unguium:

Topical

Amorolfine nail lacquer

Ciclopirox nail lacquer

Topical antifungals are used twice weekly for 6 -12 months for nail plate infections.

Oral

Terbinafine 250mg tablets once daily. The duration of therapy ranges from 6-12 weeks (fingernails) or 3-6 months (toenails).

Itraconazole 100mg capsules, 200mg once daily or 200mg bid for 7 days each month

Azole oral antifungals should be avoided in pregnancy. Removal of the nail is rarely necessary but may be considered if there is total nail destruction.