Onychomycosis

Onychomycosis, also known as tinea unguium, is a fungal infection of the nails.

Accounts for over 50% of all nail diseases, with an estimated 5.5% prevalence.

Toenails, fingernails, or both.

Differential diagnosis of onychomycosis
Differential diagnosis	Clinical features
Nail psoriasis	Shares many common clinical and histopathological features with onychomycosis Fingernails are usually more affected by psoriasis than tinea Nail pitting is the most common sign of nail psoriasis and rare in onychomycosis Nail bed ‘oil drops’: pink discolouration in the nailbed due to nailbed inflammation Other psoriatic skin changes Family history of psoriasisCan coexist with onychomycosis in 20% of people with psoriasis
Lichen planus	Typically affects several or most nails Other cutaneous features of lichen planus Pterygium unguis: Scarring between nail matrix and proximal nailfold Nail plate thinning and longitudinal ridging
Yellow nail syndrome	Association with bronchiectasis, chronic sinusitis and lymphoedema
Traumatic onychodystrophy	Usually only single nail affected Distal onycholysis
Alopecia areata	Red-spotted lunula Regularly distributed nail pitting
Age-related nail dystrophies	Onychauxis and onychoclavus can be clinically identical to onychomycosis

Who Gets It?

• Common in: Older adults (over 65), diabetics, immunocompromised patients (especially HIV), athletes.
• Family Occurrence: Possible autosomal inheritance (HLA-DR8) or environmental factors.
• Rare in Children.

Risk factors

• Predisposing Factors:
  • Chronic paronychia
  • hyperhidrosis
  • nail trauma
  • communal bathing
• Older adults: Especially those over 65 years.
• Diabetics: Higher susceptibility due to impaired immune response.
• Immunocompromised individuals: Including those with HIV.
• Athletes: Due to frequent sweating and use of communal facilities.
• Families: Some susceptibility may be hereditary (e.g., HLA-DR8) or due to shared environments.
• Children: Rare occurrence.

Associated Comorbidities:

• Tinea pedis, tinea manuum
• Psoriasis
• Peripheral vascular disease, venous insufficiency
• Hallux valgus, asymmetric gait nail unit syndrome
• Smoking
• obesity
• Down syndrome

Causes

• Dermatophytes: Majority of cases (over 75%), including various Trichophyton and Epidermophyton species.
• Non-Dermatophyte Moulds: 10% of cases, including Aspergillus and Fusarium species.
• Yeasts: Candida albicans and other non-albicans candida yeasts.
• Biofilm Role: Emerging evidence suggests its role in drug resistance and virulence.

Clinical Features

• Infection Pattern: Affects a single or multiple nails, often the first toenail.
• Nail Appearance:
  • Discoloration, thickening, jagged and crumbling edges
• Types of Onychomycosis:
  • Distal and lateral subungual
  • Superficial white
  • Proximal subungual (often HIV-related)
  • Endonyx
  • Onychauxis
• Observations:
  • Subungual hyperkeratosis
  • Jagged, crumbling nails
  • Discoloration (yellow, white, grey, green)
  • Ridging and crumbling
  • Scaling due to tinea pedis
  • Onychoma or dermatophytoma
• Candida Infection: Starts near the nail fold, can cause swelling, discoloration, and tenderness.
• Mould Infections: Similar appearance to tinea unguium.

Complications

• Quality of Life Impact: Pain, mobility issues, social stigma.

Diagnosis

• Dermoscopy: Helps differentiate from other conditions.
• Mycology Specimens: Nail clippings and scrapings for microscopy and culture.
• Histopathology: Staining techniques for fungal hyphae visualization.
• Fungal Culture Testing: Identifies causative organism.
• PCR Testing: Quick and sensitive but costly.
• Other Techniques: Exploratory methods like confocal microscopy, thermography, flow cytometry.
• Nail Biopsy: For characteristic features.

Differential Diagnosis

• Includes bacterial infections, psoriasis, lichen planus, warts, paronychia, exostosis, and malignant conditions.

Treatment

Head-to-head comparison of oral terbinafine versus azoles in onychomycosis treatment
	Terbinafine	Azoles (fluconazole and itraconazole)
Recommended line of therapy	First line	Second line
Dosage	Adult: 250 mg dailyChild <20 kg: 62.5 mg dailyChild 20–40 kg: 125 mg dailyDuration: Six weeks for fingernails, 12 weeks for toenails	Both itraconazole pulse and continuous therapy have similar efficacyPulsed itraconazole 200 mg twice daily for one week per month for two months (fingernails) and three months (toenails)Continuous itraconazole 200 mg daily for six weeks (fingernails) and 12 weeks (toenails)Fluconazole 150–300 mg once weekly for 12–24 weeks (fingernails) and 24–52 weeks (toenails)
Recurrence rate (follow-up 10–13 months)	33.3%	37.0%
Adverse effects	Gastrointestinal upset, rash, headache, myalgia	Gastrointestinal upset, diarrhoea, rash, abdominal pain, hypokalaemiaMore drug interactions than terbinafine due to its inhibition on multiple cytochrome P450 (CYP) enzymes
Recommended monitoring	Routine interval blood monitoring may be unnecessary in healthy adults and children without underlying hepatic or haematological conditions	Continuous itraconazole: Baseline liver function test (LFT) and regular LFT monitoring every four to six weeksPulsed itraconazole: none recommendedFluconazole: Baseline LFT and full blood examination; no repeat test required for once weekly therapy
Precautions	Psoriasis and lupus may be exacerbated by terbinafineContraindicated in severe hepatic diseaseDose adjustment required if CrCl <50 mL/min	Dose adjustment may be required in renal impairmentAvoid in severe hepatic diseaseFluconazole can cause prolonged QT – correct the risk factors and use with cautionItraconazole is relatively contraindicated in congestive failureItraconazole is also poorly absorbed when used with proton pump inhibitors
Pregnancy categorisation	Category B1	Fluconazole: Category D	Itraconazole: Category B3
Breastfeeding compatibility	Avoid, insufficient data	Fluconazole: compatible; may cause diarrhoea in infant	Itraconazole: avoid,

• Topical Antifungals: – nail plate is dense and keratin-rich, making it difficult for topical medications to penetrate effectively to the nail bed where the fungus reside
  • Ciclopirox
  • tavaborole
  • efinaconazole
  • amorolfine
• Oral Antifungals:
  • Terbinafine
  • fluconazole
  • itraconazole
  • posaconazole
• Non-Pharmacological:
  • Laser therapy
  • photodynamic therapy
  • iontophoresis
  • ultrasound.
• Treatment Approach:
  • Individualized, with patient counseling for cure estimation.

Prevention

• Strategies:
  • Keep feet dry
  • use flip-flops in public areas
  • manage footwear and socks
  • trim nails
  • avoid unhygienic nail practices
  • prophylactic antifungals
  • patient counseling
  • diabetes management.

Outcome and Prognosis

• Recurrence rates are 20–25%, influenced by patient age, diabetes status, immunosuppression, and severity of initial infection.