Proximal subungual onychomycosis

Proximal Subungual Onychomycosis (PSO) is a type of fungal nail infection that affects the proximal nail fold, which is the skin at the base of the nail. It is less common than other types of onychomycosis, accounting for approximately 3% of all fungal nail infections.

Causes[edit | edit source]

PSO is caused by dermatophytes, a type of fungus that infects the skin, hair, and nails. The most common species of dermatophyte involved in PSO is Trichophyton rubrum. Other species, such as Trichophyton mentagrophytes and Epidermophyton floccosum, can also cause PSO.

Symptoms[edit | edit source]

The primary symptom of PSO is a white or yellowish discoloration at the base of the nail. As the infection progresses, the nail may become thickened, brittle, and distorted. In severe cases, the nail may separate from the nail bed, a condition known as onycholysis.

Diagnosis[edit | edit source]

Diagnosis of PSO is typically made through a combination of clinical examination and laboratory testing. The KOH test, a simple and inexpensive test that uses potassium hydroxide to dissolve skin and nail tissue and reveal the presence of fungus, is commonly used. Other tests, such as fungal culture and histopathology, may also be used.

Treatment[edit | edit source]

Treatment of PSO typically involves the use of antifungal medications. Topical treatments, such as amorolfine and ciclopirox, can be effective in mild cases. However, oral antifungal medications, such as terbinafine and itraconazole, are usually required for more severe infections.

Prognosis[edit | edit source]

With appropriate treatment, the prognosis for PSO is generally good. However, the infection can be difficult to eradicate completely, and recurrence is common.