Superficial onychomycosis - Nail and Distal Digit
Onychomycosis affects up to 14% of the US population. Superficial onychomycosis is a rare subtype that is estimated to account for 1.5%-7% of cases of onychomycosis.
Superficial onychomycosis is usually seen in adults, and it is more common in immunocompromised patients, including those with human immunodeficiency virus (HIV)-infection, those with diabetes, and the elderly. Risk factors for onychomycosis and tinea pedis include hyperhidrosis, wearing occlusive footwear, and walking barefoot through public shower areas, such as in locker rooms.
Superficial white onychomycosis is generally asymptomatic, but may become painful or have a negative effect on quality of life in untreated cases. There is a high association with tinea pedis (athlete's foot), which may be pruritic. Often the initial presentation will be tinea pedis that progresses to onychomycosis over a course of weeks to months.
Pediatric Patient Considerations:
Superficial onychomycosis is rare in children.
Immunocompromised Patient Considerations:
Superficial onychomycosis is associated with an immunocompromised state, particularly HIV-infection.
B35.1 – Tinea unguium
417583002 – Superficial white onychomycosis
Differential Diagnosis & Pitfalls
- Distal subungual onychomycosis – Onycholysis and subungual hyperkeratosis. T. rubrum is often the causative agent.
- Proximal subungual onychomycosis – Look for nail plate involvement of the proximal nail; often caused by T. rubrum. Other organisms are Fusarium, Candida albicans, and Aspergillus. May be a presenting sign of HIV infection.
- Candida onychomycosis – Look for massive hyperkeratosis of the nail bed, nail plate destruction, and paronychia (periungual redness and swelling). Most commonly caused by C. albicans and seen in patients with chronic mucocutaneous candidiasis.
- Psoriasis – Look for nail pitting, oil spots, and skin involvement with psoriasis.
- Lichen planus – Look for atrophic nails, pterygium, and skin findings of lichen planus.
- Eczematous dermatitis – Look for a history of eczema, diffuse itching of the hands.
- Subungual verruca – Look for evidence of a verrucous papule under the nail.
- Nail squamous cell carcinoma – A biopsy may be necessary to rule out this entity.