Onychomycosis

Onychomycosis is a fungal infection of the nail plate, often involving the fingernails or toenails.

• It is predominantly caused by dermatophytes (Trichophyton species), though yeasts (Candida) and non-dermatophyte molds may also be implicated.

• The infection can affect one or multiple nails, leading to chronic nail dystrophy.

• High-risk populations include individuals with:

  • Diabetes mellitus

  • Peripheral neuropathy

  • Immunosuppression

  • Peripheral vascular disease

• Onychomycosis is often slow to develop, and lesions may persist for months to years without treatment.

Signs & Symptoms

• Discoloration of the nail: yellowish, white, or brown

• Subungual hyperkeratosis: thickening of the nail bed underneath the nail plate

• Onycholysis: separation of the nail plate from the nail bed

• Nail deformity: nail may become brittle, crumbly, or irregularly thickened

• Progression: lesions gradually spread along the nail, potentially affecting the entire nail plate

• Occasional discomfort or mild pain, particularly with toenail involvement

Diagnostic Criteria

• Clinical examination revealing:

  • Yellowish or brown discoloration of the nail

  • Subungual hyperkeratosis

  • Gradual thickening, crumbling, or deformity of the nail

• Typical sites: toenails more commonly than fingernails

• Chronic progression without acute inflammation

• In uncertain cases, laboratory confirmation with KOH preparation, fungal culture, or nail biopsy may be required

Investigation

• Direct microscopy: KOH mount to detect fungal hyphae

• Fungal culture: to identify causative organism and guide therapy

• Histopathology (PAS stain): useful for atypical cases or mixed infections

• Laboratory tests: baseline liver function tests prior to systemic antifungal therapy, especially in patients on long-term oral medications

Treatment

Non-Pharmacological Treatment

• Nail care: trimming and filing thickened nails

• Foot hygiene: keep nails dry, avoid trauma, change socks daily

• Environmental precautions: disinfect nail clippers and footwear

• Avoid sharing personal items to reduce transmission

Pharmacological Treatment

Systemic therapy is often required, especially for toenails or extensive disease:

First-line oral antifungals:

• Terbinafine (PO): 250 mg daily

  • Duration:

    • Fingernails: 6–8 weeks

    • Toenails: 12–16 weeks

  • Highly effective against dermatophytes

Alternative oral regimens:

• Itraconazole (PO) pulsed dosing: 200 mg twice daily for 1 week per month for 6 months

• Fluconazole (PO): 150–300 mg once weekly for 6–12 months

Notes:

• Fingernail infections generally require 2 months of therapy, whereas toenails require 4 months due to slower growth

• Monitor liver function during systemic therapy

• Topical antifungals may be considered for mild or superficial infections, but limited efficacy for full nail involvement

Prevention

• Maintain good nail hygiene

• Keep nails dry and trimmed

• Avoid trauma to nails

• Wear protective footwear in communal areas

• Avoid sharing nail clippers or footwear

• Manage underlying conditions such as diabetes or peripheral vascular disease