Tinea Unguium

Definition

Tinea unguium, also known as onychomycosis, is a fungal infection of the nail caused by dermatophytes, yeasts, or non-dermatophyte molds, leading to nail thickening, discoloration, and dystrophy.

Epidemiology

• Common in adults, especially older individuals; prevalence increases with age.
• More common in toenails than fingernails.
• Risk factors: diabetes, immunosuppression, peripheral vascular disease, trauma, occlusive footwear, and athlete's foot.
• Affects approximately 10% of the general population, higher in elderly and diabetic patients.
• More frequent in males than females.

Etiology

• Dermatophytes: *Trichophyton rubrum*, *T. mentagrophytes* (most common).
• Yeasts: *Candida* species (especially fingernail infections).
• Non-dermatophyte molds: *Scopulariopsis*, *Fusarium* (less common).
• Transmission: direct contact with infected nails, skin, or contaminated surfaces.

Pathophysiology

• Fungi invade the nail plate, nail bed, or subungual area, metabolizing keratin.
• Induces local inflammatory response, causing nail thickening, discoloration, and crumbling.
• Chronic infection can lead to onycholysis, subungual debris accumulation, and secondary bacterial infection.
• Toenails are more affected due to slower growth and occlusive footwear.