Definition:

Onychomycosis is a fungal infection of the nails, typically caused by dermatophytes, but can also involve yeasts and non-dermatophyte molds. It most commonly affects the toenails but can also involve fingernails.

Types:

1. Distal Lateral Subungual Onychomycosis (DLSO):

   • Most common type

   • Starts at the nail bed and spreads under the nail plate.

2. White Superficial Onychomycosis (WSO):

   • Fungal invasion of the top layers of the nail plate.

   • Appears as white, chalky spots.

3. Proximal Subungual Onychomycosis (PSO):

   • Infection starts near the cuticle.

   • Often seen in immunocompromised patients.

4. Candidal Onychomycosis:

   • Caused by Candida species.

   • Often affects fingernails and associated with paronychia.

5. Total Dystrophic Onychomycosis (TDO):

   • Complete destruction of the nail plate.

   • Usually the end-stage of other types.

Causes:

• Dermatophytes (Trichophyton rubrum, T. interdigitale)

• Yeasts (Candida albicans)

• Non-dermatophyte molds (Scopulariopsis, Fusarium)

• Risk factors include:

  • Poor foot hygiene

  • Diabetes

  • Immunosuppression

  • Wearing occlusive footwear

  • Nail trauma

Symptoms:

• Thickened nails

• Discolored nails (yellow, white, or brown)

• Brittle, crumbly, or ragged nails

• Distorted nail shape

• Separation of the nail from the nail bed (onycholysis)

• Foul smell

• Pain or discomfort in severe cases

Diagnosis:

• Clinical examination

• KOH (potassium hydroxide) preparation

• Fungal culture

• Nail biopsy or PCR testing in difficult cases

Treatment:

Topical Antifungals (mild cases):

• Ciclopirox lacquer

• Amorolfine

• Efinaconazole

• Tavaborole
  Note: Daily use for months; limited efficacy for deeper infections.

Oral Antifungals (moderate to severe cases):

• Terbinafine – 250 mg/day for 6–12 weeks

• Itraconazole – Pulse therapy or continuous therapy

• Fluconazole – Less commonly used

Other Treatments:

• Laser therapy (emerging treatment)

• Surgical nail removal (in severe, painful cases)

• Photodynamic therapy

Prevention:

• Keep nails trimmed, clean, and dry

• Avoid walking barefoot in communal showers or pools

• Wear breathable footwear

• Disinfect nail tools regularly

• Avoid sharing towels or nail clippers

Prognosis:

• Can be cured with treatment, but recurrence is common

• Long treatment duration (months)

• Better outcomes with early diagnosis and combined therapies