High Yield Topics

Onychomycosis

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Ovid: 5-Minute Sports Medicine Consult, The


Onychomycosis
John T. Swisher IV
Suzanne Hecht
Basics
Description
  • A fungal infection of the toes and/or fingernails involving the nail bed, matrix, or plate
  • Synonym(s): Nail ringworm; Tinea unguium
Epidemiology
  • 22–130 cases/1,000 population
  • Accounts for 1:3 of integumentary infections
  • Incidence of infection increasing worldwide
  • Accounts for 50% of toenail dystrophies
  • Adults 30× more likely to be affected than children
  • ∼2% prevalence in children
Risk Factors
  • HIV
  • Immunosuppressive states
  • Diabetes mellitus (DM)
  • Contact with infected individuals
  • Peripheral vascular disease (PVD)
  • Trauma
  • Communal bathing
  • Occlusive footwear
General Prevention
  • Appropriate foot hygiene:
    • Wear absorbent cotton socks.
    • Wear breathable footwear.
    • Protect feet in community areas.
    • Keep feet dry throughout day.
  • Discard old shoes that may harbor fungi.
  • Control chronic health conditions.
Etiology
  • Pathophysiology:
    • Distal/lateral subungual onychomycosis (most common): Fungal invasion begins at hyponychium and spreads along nail bed proximally, concomitantly involving the inferior nail plate.
    • White superficial onychomycosis: Fungal invasion develops from dorsal nail plate invasion.
    • Proximal subungual onychomycosis (associated with immunocompromised state): Fungal invasion of cuticle and subsequent nail fold that penetrates dorsal nail plate
    • Endonyx onychomycosis (least common): Fungal invasion of nail surface with eventual deep penetration
    • Candidal onychomycosis: Yeast infection via onycholysis, paronychia, or chronic mucocutaneous disease
    • Total dystrophic onychomycosis: End-stage fungal infection of entire nail unit that may easily fragment and lead to permanent scarring
  • Etiology:
    • Dermatophytes (>90% occurrence rate)
    • Yeast
    • Nondermatophytes
Diagnosis
History
  • Identify digits involved.
  • History of predisposing factors: Trauma, tinea, and immunocompromised state
  • Discuss bathing footwear habits
  • Historical clues in regard to secondary infection
Physical Exam
  • Distal/lateral subungual onychomycosis: Thickened/opacified nail with possible subungual hyperkeratosis and/or onycholysis
  • White superficial onychomycosis: White patches on nail surface that can coalesce
  • Proximal subungual onychomycosis: Nail fold leukonychia with white proximal nail plate
  • Endonyx onychomycosis: White nail plate without subungual hyperkeratosis or onycholysis
  • Candidal onychomycosis: Paronychia, onycholysis, and/or subungual hyperkeratosis
  • Total dystrophic onychomycosis: Thick, opaque, yellow-brown nail involving entire plate/matrix
Diagnostic Tests & Interpretation
  • Diagnosis made when both clinical and laboratory results are positive
  • Essential that causative organism is identified
  • Avoid topical antifungals for 2 wks prior to testing.
  • Cleanse nail with alcohol swab prior to testing.
  • Utilize potassium hydroxide (KOH) and fungal culture to determine therapy for initial screen.
    • Owing to a high false-negative rate, you may need to repeat KOH or use histologic analysis with fungal culture.
    • Histologic analysis with periodic acid–Schiff (PAS) is more sensitive than KOH or culture (1)[A].
Lab
  • KOH prep with light microscopy:
    • 20% KOH with 40% dimethyl sulfoxide (DMSO)
    • Use a 1-mm curette to obtain most proximal sample
    • Use a No. 15 blade scalpel for superficial fungi.
    • Immediate results
  • Fungal culture:
    • Cycloheximide medium for dermatophytes and noncycloheximide medium for yeasts and nondermatophytes
    • Nail clippings or scrapings for specimen
    • May take weeks to grow on medium
    • Species identification
  • Histologic analysis with PAS:
    • High sensitivity
    • Prompt results
    • Pathogen not identified
    • Distal nail clipping from attachment to nail bed in formalin
  • Immunohistochemistry:
    • Identifies pathogen via labeled antibody to specific fungi
    • Complicated and costly
  • In vivo confocal microscopy:
    • Uses light to penetrate nail to analyze reflection of fungi
    • Inability to distinguish pathogen
    • Costly
  • Scanning electron microscopy:
    • Expensive
    • Detailed imaging of fungi elements
  • Polymerase chain reaction (PCR):
    • Fungal species identification by DNA sequence analysis
    • Sufficient nail material required for testing
  • Flow cytometry:
    • Sorts by DNA, protein, cell size, and granulosity to identify fungi
    • Complicated and costly
Differential Diagnosis
  • Eczema
  • Endocrine disease
  • Herpes whitlow
  • Malignant melanoma
  • Medications
  • Paronychia
  • Psoriasis
  • Squamous cell carcinoma
  • Trauma
  • Yellow nail syndrome

P.417


Treatment
  • Indications for treatment consist of pain, functional limitation, aesthetic purposes, and secondary infection.
  • Discuss costs, side effects, and continuous/pulse dosing.
  • Confirm past medical history to determine appropriate medication.
  • Treat tinea pedis as soon as possible.
  • Explain that it may take 12–18 mos for resolution of toenail infections and 4–6 mos for resolution of fingernail infections.
  • Despite successful eradication of fungi, the nail may remain abnormal in appearance. This is not considered a treatment failure.
  • Clinical cure is based on the absence of physical exam findings.
  • Mycologic cure is when no fungal elements remain; however, the nail appearance still may be abnormal.
  • Repeat testing may be required at completion of treatment to confirm cure.
  • High recurrence (relapse/reinfection) rates: 15–20% within 1 yr
  • Treatment failure may require repeat treatment.
  • Return to play ± oral, topical, or surgical treatment is based on symptoms.
Medication
First Line
Terbinafine:
  • Fungicidal against dermatophytes with fungistatic properties against some yeast and nondermatophytes
  • Mycologic cure 76% ± 3%; clinical cure 66% ± 5%
  • Fingernail: 250 mg/day × 6 wks (2)[A]
  • Toenail: 250 mg/day × 12 wks (2)[A]
  • Monitor pretreatment AST/ALT and every 6 wks for hepatotoxicity
  • Contraindications: Hypersensitivity
  • Precautions: Hepatotoxicity, GI upset, immunodeficiency, systemic lupus erythematosus (SLE), renal insufficiency, Steven-Johnson syndrome, and drug interactions
Second Line
  • Itraconazole:
    • Fungistatic against dermatophytes, yeast, and nondermatophytes
    • Mycologic pulse cure 63% ± 7%; mycologic continuous cure 59% ± 5%; clinical pulse cure 70% ± 11%; clinical continuous cure 70% ± 5%
    • Fingernail continuous therapy: 200 mg/day × 6 wks (3)[A]
    • Toenail continuous therapy: 200 mg/day × 12 wks (3)[A]
    • Fingernail pulse therapy: 200 mg b.i.d. × 7 days, off 21 days (2–3 pulses may be required)
    • Toenail pulse therapy: 200 mg b.i.d. × 7 days, off 21 days (3–4 pulses may be required)
    • Monitor pretreatment AST/ALT and every 6 wks for hepatotoxicity for continuous therapy; not required for pulse therapy
    • Contraindications: Hypersensitivity, pregnancy, ventricular dysfunction, concomitant use of CYP3A4 drugs
    • Precautions: Hepatotoxicity, GI upset, hearing loss, neuropathy, drug interactions
  • Griseofulvin:
    • Fungistatic against dermatophytes
    • Mycologic cure 60% ± 6%; clinical cure 2% ± 2%
    • Fingernails: 1,000 mg/day × 4 mos or more (3)[A]
    • Toenails: 1,000 mg/day × 6 mos or more (3)[A]
    • Contraindications: Hypersensitivity, porphyria, hepatocellular dysfunction, pregnancy
    • Precautions: Penicillin allergy, photosensitivity
  • Ciclopirox 8%:
    • Mechanism of action unproven
    • Mycologic cure 32%; treatment cure 7%
    • Apply daily × 48 wks; remove lacquer once a week (2)[A].
    • Consider when oral medication isn't indicated or nail plate has been removed.
    • Contraindication: Hypersensitivity
    • Precautions: DM, immunosuppressed state, and concomitant systemic antifungal use
Surgery/Other Procedures
  • Nail plate removal (total or partial)
  • Chemical removal (40% urea)
  • Use concomitant oral or topical antifungal with surgical approach (4)[C].
  • Consider in recalcitrant cases.
References
1. Bell SS, Hall JB. Oral treatments for toenail onychomycosis (protocol). The Cochrane Collaboration 2009.
2. Gupta AK, Tu LQ. Therapies for onychomycosis: a review. Dermatol Clin. 2006;24:375–379.
3. Internet Resource: Thompson Micromedix Healthcare Series.
4. Blumberg M, Kantor GR. www.emedicine.com. Onychomycosis. 2007.
Codes
ICD9
  • 110.1 Dermatophytosis of nail
  • 112.3 Candidiasis of skin and nails
Clinical Pearls
  • Not all nail dystrophies are due to fungi.
  • Clinical and lab confirmation is essential for appropriate diagnosis and treatment.
  • Oral is favorable to topical treatment.
  • High recurrence rates exist.
  • Advise patient on prevention techniques.


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