Onychomycosis
Onychomycosis is Tinea unguium or fungal infection of the nail. Tinea unguium usually occurs in tandem with tinea pedis. It is recognized by nail thickening and separation from nail bed (onycholysis).
CASES/YEAR
269,700 (US); 5,394,000 (Global)
AGENT TYPE
Fungi (Dermatophytes)
OTHER NAMES
Tinea unguium;
INCUBATION
Unknown; [CCDM, p. 229]
INITIAL SYMPTOMS
Nail thickening and separation from nail bed (onycholysis);
PRECAUTIONS
"Low rate of transmission, even to close family associates." [CCDM, p. 233]
COMMENTS
Onychomycosis is called tinea unguium when it is caused by dermatophytes with the most common ones being Trichphyton rubrum, Trichphyton. Mentagrophytes var. interdigitale, and Epidermophyton floccosum. Tinea unguium usually occurs in tandem with tinea pedis. Distal subungual onychomycosis is the most common type, followed by superficial white onychomycosis. Proximal subungual onychomycosis is the rarest type, and it is associated with HIV infection. Other causes of onychomycosis are Candida infection in patients with chronic mucocutaneous candidiasis and nondermatophyte mold infections caused by Aspergillus, Fusarium, and Scytalidium species. Psoriasis causes onycholysis and nail pitting. [ID, p. 1170-2; PPID, p. 3206] Dermatophytes cause >80% of onychomycosis infections. The prevalence of onychomycosis in the elderly (> 70 years) is up to 48%. [ABX Guide] Secondary bacterial infections can progress to osteomyelitis. [5MCC-2020] The infected nail thickens, separates from the nail bed, becomes discolored and chalky, and eventually disintegrates. [CCDM, p. 233] Psoriasis causes nail changes that may resemble onychomycosis. Psoriasis usually causes other skin lesions. [Harrison ID, p. 1030]
DIAGNOSTIC
Only 50% of cultures confirm onychomycosis; Clinical (discoloration of nails and evidence of tinea pedis); KOH exam; Culture of nail clippings/subungual scrapings (more sensitive than KOH prep); Nail clippings for histological analysis; [ABX Guide]
ENTRY
Skin or Mucous Membranes (Includes Conjunctiva)
TREATMENT
"Terbinafine (250 mg per day) for 2 (fingernails) or 3 (toenails) months is the most effective treatment for dermatophyte infections." [Cecil, p. 2662] Note any pre-existing liver disease--check baseline liver function tests and CBC. "LFT monitoring needed only if initial LFTs abnormal or preexisting liver disease or concomitant use of drugs with potentially additive hepatotoxicity. Very few drug interactions and very well tolerated." [ABX Guide]
REFERENCES FOR CASES/YEAR
1. (US) !/20 X global cases/yr;
2. (Global) An estimated 2-13& of the general population have onychomycosis. [Guerrant, p. 562] Tinea unguium was 31% of dermatomycoses in Japan; Using incidence results from study in New Zealand in 2003 showing 2900 cases of dermatomycoses per million; 0.31 X 2900 = 899 cases per million; 899/million X 6000 million = 5,394,000 cases per year (worldwide); [PMID 23149353 & 14616492]