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B35.1 – Tinea unguium
414941008 – Onychomycosis
SynopsisOnychomycosis is a fungal infection of the nail caused by dermatophyte fungi (tinea unguium), nondermatophyte molds, or yeasts. Onychomycosis is more frequent in men and is commonly associated with concurrent tinea pedis. It affects toenails more commonly than fingernails, and fingernail infection is typically preceded by or associated with toenail infection. Onychomycosis is classified into 3 patterns relating to the site of invasion of the nail: distal lateral subungual, superficial white, and proximal subungual.
Distal lateral subungual onychomycosis (DLSO) is the most common form of onychomycosis and begins with fungal invasion of the distal nail (hyponychium). In Western countries, DLSO is mainly due to Trichophyton rubrum.
Superficial white onychomycosis (SWO) is due to fungal invasion of the superficial dorsal nail plate, typically caused by T. rubrum in HIV-infected patients and Trichophyton mentagrophytes in immunocompetent individuals.
Proximal subungual onychomycosis (PSO) is caused by invasion of the proximal nail fold. In the absence of paronychia, PSO is typically due to T. rubrum.
While Candida species are frequently cultured from nails, these species are not thought to be the primary pathogen. Candida is commonly associated with chronic paronychia and occasionally secondarily infects the nail plate. True nail invasion by Candida is seen almost exclusively in chronic mucocutaneous candidiasis.
Immunocompromised Patient Considerations:
SWO and PSO have been reported to be more common in HIV infection and immunocompromised states.
Majocchi-like granulomas, deep ulcerated fungal infections, severe tinea capitis and corporis, and fungal nail involvement are characteristic of an inherited deficiency of CARD9 (caspase recruitment domain-containing protein 9), an inflammatory cascade-associated protein. The disorder is autosomal recessive and is most common in North Africa countries including Algeria, Morocco, and Tunisia. The infections usually begin in childhood and are caused by T. rubrum and Trichophyton violaceum. Lymphadenopathy, high IgE antibody levels, and eosinophilia are common, and the disorder can be fatal.