Distal subungual onychomycosis

Distal Subungual Onychomycosis (DSO) is a type of fungal nail infection that affects the nail bed and underside of the nail plate. It is the most common form of onychomycosis and is primarily caused by dermatophytes, particularly Trichophyton rubrum.

Etiology

DSO is primarily caused by Trichophyton rubrum, a type of dermatophyte. Other dermatophytes such as Trichophyton mentagrophytes and Epidermophyton floccosum can also cause DSO. In rare cases, non-dermatophyte molds and yeasts like Candida species can cause DSO.

Clinical Presentation

DSO typically begins at the distal edge of the nail and progresses towards the cuticle. Early symptoms include discoloration of the nail, often yellow or white, and thickening of the nail. As the infection progresses, the nail may become brittle and crumble, and there may be pain and inflammation of the surrounding skin.

Diagnosis

Diagnosis of DSO is typically made through clinical examination and confirmed through laboratory tests. These may include potassium hydroxide (KOH) preparation, fungal culture, or histopathological examination using periodic acid-Schiff (PAS) staining.

Treatment

Treatment of DSO typically involves antifungal medications. These may be topical, such as amorolfine or ciclopirox, or systemic, such as terbinafine, itraconazole, or fluconazole. In severe cases, surgical removal of the nail may be necessary.

Prognosis

With appropriate treatment, the prognosis for DSO is generally good. However, recurrence is common, particularly in individuals with predisposing factors such as diabetes, peripheral vascular disease, or immunosuppression.

Prevention

Prevention of DSO involves maintaining good foot hygiene, avoiding trauma to the nails, and wearing breathable footwear. Individuals with a history of DSO may benefit from prophylactic use of antifungal medications.