Fungal infections of the fingernails or toenails are common globally and relatively mild, but can have an impact on quality of life (Gupta & Mays, 2018). In rare cases they can spread to other tissues in severely immunocompromised individuals.
Specimen collection is of great importance to achieving the correct diagnosis and choice of treatment depends on which species is involved.
Patterns of onychomycosis
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Onychomycosis; tinea unguium; fungal infection of the nails; paronychia
Fungi may affect the nail fold (paronychia) or the nail itself (onychomycosis). Toenails are more commonly affected than fingernails. Discolouration of the nail, either in part of completely is typical.
Paronychia is usually caused by Candida albicans and occasionally other Candida species. Onychomycosis is caused by a wide variety of fungi especially T. rubrum, which causes about 80% of cases in the UK. Non-dermatophyte moulds that occasionally cause onychomycosis, usually of the toenail, include Fusarium spp., Aspergillus spp. (reviewed by Bongomin et al, 2018), Acremonium spp., Alternaria alternata, Scytalidium dimidiatum, Scytalidium hyalinum (Nattrassia mangiferae), Scopulariopsis brevicaulis and Onychocola canadensis. C. albicans and, rarely, Candida parapsilosis cause onychomycosis, especially superficial white onychomycosis. Some infections are caused by more than one fungus.
Fungal nail infection (onychomycosis) is common in the general adult population, probably 5-25% rate with an increasing incidence in elderly people. Onychomycosis makes up about 30% of all skin, hair and nail fungal infections, so approximately 300 million are affected.
Patients with AIDS may present with onychomycosis, especially superficial white onychomycosis. Candida paronychia is more common in those with extensive water contact with their hands. Onychomycosis caused by Fusarium spp. may lead to disseminated infection in leukaemia patients.
Scraping of the nail itself, or the material under the nail is the most rewarding material. Microscopy (Velasquez-Agudelo & Cardona-Arias, 2017) and fungal culture. PCR for T. rubrum in some institutions. Dermoscopy (Yorulmaz & Yalcin, 2018)
Candida paronychia, when mild and localised, will usually respond to imidazole or terbinafine cream or nystatin ointment applied topically for 1–3 weeks. Very localised distal nail infection may respond topical amorolfine or ciclopirox, but results are inferior to oral therapy. Oral therapy with terbinafine or itraconazole for many weeks or months is 80+% effective. Griseofulvin is over 80% effective for fingernail onychomycosis, but less than 40% effective for toenail disease. Topical amphotericin B in a 50:50 (v/v) mixture of dimethylsulphoxide and 2-propanol at a final concentration of 2 mg/ml may be effective for susceptible fungi such as Fusarium and Acremonium. 1-3 drops are applied daily and allowed to dry, for 12+ months. Urea-based cream allows softening of the nail and improved penetration of topical agents. Nail removal is sometimes necessary, and always so for infections caused by Scopulariopsis or Scytalidium. Laser treatment is a more recent treatment (Ma et al, 2019).
– A Cochrane review is available for oral antifungals in onychomycosis (Kreijkamp-Kaspers et al, 2017)
Cure is possible, but takes a long time, as the growth of the nails is slow.