Onychomycosis (Fungal Nail Infection / Tinea Unguium)

Onychomycosis is a slowly progressive infection of the nails, often taking months to years to develop. Patients usually present due to cosmetic concern or due to the nail becoming:

• Thickened and difficult to cut.

• Discoloured (yellow, off-white, brown, or grey).

• Crumbly or lifting from the nail bed (onycholysis), with debris underneath.

The condition is often asymptomatic, but patients may report mild discomfort or pressure, especially from tight shoes.

Associated Risk Factors:

• Tinea pedis (Athlete's foot) is a major risk factor, often coexisting.

• Comorbidities: Diabetes, peripheral vascular disease, immunosuppression, and psoriasis.

• Local Factors: Chronic trauma, tight or occlusive footwear, and frequent exposure to communal showers or nail salons.

Crucial Note for Darker Skin Tones: 

Patients may focus on the colour change, reporting a "dark or dirty-looking nail" rather than classic inflammation. A high cosmetic impact is common, sometimes influencing footwear choices. It is vital to rule out subungual melanoma if new, changing, or irregular pigmentation is reported, particularly in the presence of physiological melanonychia (normal brown bands).

The infection is primarily seen on the toenails (often starting with the great toenail), but fingernails may also be affected.

General Findings:

• Thickened, rough, and dystrophic (abnormally formed) nail plate.

• Discolouration: The nail may appear yellow, white, or brown. Green or black discolouration suggests secondary infection.

• Onycholysis: The nail plate is separated from the nail bed, with excessive subungual hyperkeratosis (crumbly, keratinous debris) trapped underneath.

• The distal free edge is often jagged and crumbling.

Associated Findings: Always check the skin for tinea pedis (scaling on the soles or maceration between the toes).

Diagnosis Confirmation: Clinical appearance is unreliable. Nail clippings or scrapings must be taken from the most proximal diseased area for:

• KOH microscopy (to visualize hyphae).

• Fungal culture (to identify the organism).

• This is necessary to differentiate onychomycosis from other conditions like nail psoriasis, trauma, or subungual tumours.

Key Considerations in Darker Skin Tones:

• Nail Colour: The colour changes may appear more brown or grey than the classic yellow.

• Pigmentation: The presence of physiological melanonychia (benign pigmented bands) can overlap with fungal infection, making clinical diagnosis difficult and increasing the risk of missing a subungual melanoma if the pigmentation is irregular or involves the nail fold.

• Inflammation: Surrounding skin inflammation (paronychia) may show less obvious redness; rely on swelling, tenderness, and warmth for assessment.

Treatment is chronic, requiring months of compliance, and is guided by the extent of the disease and the specific organism.

1. General Measures / Self-care:

• Maintain good hygiene: keep nails short, clean, and dry.

• Disinfect nail clippers and wash hands after use.

• For toenails: Wear breathable footwear and always wear protective footwear in communal wet areas (showers, pools). Treat any associated tinea pedis concurrently.

2. Topical Therapy (Mild / Limited Disease): Topicals are best for involvement of one or two nails, affecting less than 50% of the nail, and with no matrix involvement.

• Options: Ciclopirox 8% lacquer, Amorolfine 5% lacquer, or newer solutions like Efinaconazole.

• Regimen: Requires daily application for many months (often 6–12 months) until a completely normal nail has grown out. Urea cream can be used adjunctively to thin the nail.

3. Oral Antifungal Therapy (Moderate–Severe Disease): Provides the best chance of cure and is necessary for multiple nails, matrix involvement, or severe toenail disease.

• Common Agents: Terbinafine, Itraconazole, or Fluconazole.

• Monitoring: Baseline and periodic Liver Function Tests (LFTs) and blood counts are required due to the risk of hepatotoxicity. Drug-drug interactions must be reviewed carefully.

4. Procedural Options:

• Mechanical debridement by a podiatrist helps thin the nail, reducing discomfort and improving drug penetration.

• Surgical or chemical nail avulsion (removal) may be used for very stubborn or painful cases.

Counselling for Darker Skin Tones:

• Patience: Emphasize that visible improvement is slow: 6 months for fingernails and 12–18 months for toenails.

• Cosmetics: Discuss realistic cosmetic outcomes, as pre-existing melanonychia or chronic trauma may prevent the nail from returning to a completely "normal" appearance.

• Differential Diagnosis: Reinforce the need for accurate diagnosis (culture/biopsy) to avoid unnecessary aggressive treatment of benign pigmented nails.

Skinsight – Onychomycosis (Adult): https://skinsight.com/skin-conditions/onychomycosis/

DermNet NZ – Fungal Nail Infections (Onychomycosis): https://dermnetnz.org/topics/fungal-nail-infections