EDUCATION & DEBATE Fortnightly Review
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EDUCATION & DEBATE Fortnightly Review Fungal nail disease: a guide to good practice (report ofa Working Group ofthe British Society for Medical Mycology) D W Denning, E G V Evans, C C Kibbler, M D Richardson, M M Roberts, T R Rogers, D W Warnock, R E Warren The term onychomycosis refers to fungal infection of the nails whether this is a primary event or a secondary Summary points infection of a previously diseased or traumatised nail. Infection may be due to dermatophyte (ringworm, * Onychomycosis is usually caused by tinea unguium), yeast, or other non-dermatophyte dermatophytes (85-90%), but several fungi that (mould) species, and the clinical appearance may are difficult to treat affect toenails indicate the nature of the infecting organism. In * Paronychia is caused by many Candida paronychia chronic infection of the nail fold is most species, some resistant to azole drugs Department ofInfectious often caused by Candida species, but bacterial Diseases and Tropical infection with Gram negative species such as Pseudo- * Samples for mycology should be taken as Medicine (Monsall Unit), proximally as possible in the nail North Manchester General monas may coexist. Acute paronychia (whitlow) due to Hospital, Manchester staphylococcal infection may also occur, and the * Demonstration of hyphae in a nail specimen MS SRB presence of these bacterial infections will influence by microscopy is sufficient to start treatment D W Denning, senior lecturer management. Invasion of the nail plate by Candida * Choice of treatment depends on many factors species may occur in the presence of paronychia, including patient's age and preference, infecting PHLS Mycology Reference immune deficiency states (including chronic muco- fungus, number of nails affected, degree of nail Laboratory, Department of cutaneous candidiasis), Raynaud's disease, or involvement, whether toenails or fingernails are Microbiology, University endocrine disorders. infected, and other drugs being taken ofLeeds This paper reviews the clinical features of onycho- E G V Evans, head mycosis and the differential diagnosis ofnail dystrophy, Department ofMedical gives the reasons for appropriate mycological investi- Microbiology, Royal Free gation, and discusses guidelines for appropriate recent population survey of dermatophyte onycho- Hospital, London treatment on the basis of laboratory findings and mycosis has suggested a prevalence of 2-8% for men C C Kibbler, consultant particular clinical situations. and 2-6% for women in the United Kingdom.' Earlier surveys of swimming pools,4 schools,5 hospital Regional Mycology patients,6 and office workers7 have shown a prevalence Reference Laboratory, Epidemiology of tinea pedis of 8-40%. Of those people with tinea Department of Treating onychomycoses is difficult but is important pedis, 20-30% also have affected nails.8 This suggests of Dermatology, University because do not resolve About that the of in adults could Glasgow they spontaneously. 30% prevalence onychomycosis M D Richardson, head of all superficial fungal infections affect the nail.'2 A therefore be about 3-8%. This is difficult to assess, however, since some reports do not distinguish University Department of between dermatophytosis and other forms of onycho- Dermatology, Hope mycosis or between infection of fingernails and toe- Hospital, SalfordM6 SMD Box 1: Causes offungal nail infection nails. M M Roberts, consultant Common Uncommon Toenails are more commonly infected than finger- Dermatophytes nails.' This applies particularly to dermatophyte and Department ofInfectious Tichophyton rubrum Trichophyton erinacei mould infections, whereas Candida infections are more Diseases and Bacteriology, Trichophyton interdigitale Trchophyton soudanense Royal Postgraduate likely to affect the fingernails and fingernail folds.'" Trichophyton tonsurans Mixed infection can account for up to 5% of Medical School, London Tichophyton violaceum onycho- T R Rogers, professor Epiderinophytonfloccosum mycotic infections.'12 There is wide geographical and Microsporum canis ethnic variation in the causative species, but in Britain PHIS Mycology Reference Yeasts about 5% ofcases are due to non-dermatophyte moulds Laboratory, Public Health Candida albicans Candida glabrata * such as Scopulariopsis (see box 1) and these almost Laboratory, Bristol Candida parapsilosis Candida guillermondii exclusively affect nails. There are many cases of D W Warnock, head Candida krusei* patients who have been inappropriately treated for Candida tropicalis years because the correct diagnosis has not been Public Health Laboratory, Non-dermatophytes (moulds) established. Nail infection due to will Royal Shrewsbury Hospital Scopulariopsis Fusarium spp Aspergillus spp not respond to the standard treatments for dermato- R E Warren, director Scopulariopsis brevicaulis Acremonium spp Scytalidium dimidiatum phyte or yeast onychomycosis. Correspondence to: (Hendersonula) The increase in foreign travel has led to the intro- Dr Roberts. Scytalidium hyalinum duction of some exotic species. In addition fungi *Primanly causes ofparonychia. previously considered to be non-pathogenic may now BAM 1995;311:1277-81 be found as pathogens in patients with immune BMJ VOLUME 311 1 1 NOVEMBER 1995 1277 Clinical appearance Box 2: Typical cHnical appearance of The clinical picture of a fungal nail infection varies fungal nail dystrophy according to the nature of the infecting organism (see box 2). Involvement of adjacent skin should be noted, Dermatophyte since ifthis is due to fungal infection the treatment may Distal and lateral nail involvement spreading proximally or be different. If fungal infection is included in the Proximal subungual dystrophy or differential diagnosis then mycological examination is Superficial white dystrophy essential, even if another disease exists. Non- White or yellow thickened nails, crumbling of nail dermatophyte moulds may be present as a secondary plate invader if a nail has previously been diseased or Adjacent web or skin involvement may be present traumatised. This may account for the fact that such Candida infections often affect only one nail. Chronic paronychia Distal or lateral involvement of the nail plate Shiny red bolstered nail fold occurring at the free end of the nail and spreading Almost exclusively affects fingernail folds proximally is particularly associated with Trichophyton Loss ofcuticle rubrum infection or some non-dermatophyte infections. Pus exuding from under nail fold Eventually the whole nail may be affected, and there Usually proximal nail involvement may be proximal subungual nail dystrophy with Distal nail dystrophy-associated with circulatory separation of the nail from the bed. In superficial disorders white onychomycosis, crumbly white areas are evident Total dystrophic onychomycosis-chronic muco- cutaneous candidosis on the nail surface particularly in patients with Nails white, green, or occasionally black AIDS. T interdigitale causes this type of appearance. Paronychia is seldom present in a dermatophyte Non-dermatophyte infection, but Candida infection often begins in the Superficial white onychomycosis proximal nail plate and paronychia is common. In Often solitary nail involvement-more often toenail chronic mucocutaneous candidosis, a rare T cell dis- Colour ofnail may be influenced by nature of infecting mould. For example: order with disabling mucosal candidiasis, total nail Acremonium spp-superficial white onychomycosis dystrophy is usual. Scopulariopsis spp-white, yellow, brown, or green Scytalidium spp-white or black Fusatium spp-white Differential diagnosis Alternaria spp-brown Several conditions may be associated with nail Aspergillus spp-green or black dystrophy, including bacterial and fungal infection (see box 3). Sometimes bacterial infection may coexist with fungal infection and may require treatment in its deficiency and are often associated with a high own right. Many other conditions can cause a change in mortality. For example, Fusarium species may cause the appearance ofthe nail, but the nail surface does not onychomycosis, usually with a solitary toenail usually become soft and friable as in a fungal infection. infection and sometimes with paronychia. This If there is any doubt a specimen should be taken for may provide a portal of entry leading to dissemi- mycological examination. nated infection in immunocompromised patients, In some cases of psoriasis and eczema there may be particularly those with haematological conditions fungal superinfection of the nails. Yeasts and bacteria and AIDS. are often found in subungual debris from psoriatic Box 3: Non-fimgal conditions particularly associated with nail dystrophy Bacterial nail infection Lichen planus Pseudomonas aeruginosa-green or black dis colour- Pterygium formation from cuticle ation Longitudinal ridging ofnails Staphylococcus aureus may present as acute paronychia Total nail loss, usually permanent (whitlow) May be lichen planus elsewhere Onychogryphosis Alopecia areata and alopecia totalis Grossly thickened and distorted horn-like appearance Solitary or multiple nail dystrophy ofnail Variable severity ofnail dystrophy Overcurvature ofnail Diffuse fine pitting, often in transverse lines Great toenails most commonly affected Frequent onychorhexis (fragmented nails) and ridging May follow trauma Onset ofnail dystrophy may not coincide with hair loss Psoriasis Yellow nail syndrome Yellow friable nails with pitting and onycholysis Slow growing nails (lifting ofnail from bed) Smooth overcurved