Scytalidium hyalinumonychomycosis successfully treated with 5% amorolfine nail lacquer

S ir, Scytalidium hyalinum is a rare onychomycosis in temperate climates. Most cases in the U.K. occur in immigrants from tropical countries or in those with a history of a holiday in such places.1 This geophilic non‐dermatophyte mould is usually a plant pathogen but can be a primary pathogen of skin and nails.2 It is the most common cause of athlete's foot in South‐east Asia. This particular fungus often exists in a coinfection with dermatophytes.2,S. dimidiatum (previously called Hendersonula toruloidea) is currently thought to be a variant of S. hyalinum. The former is a black fungus which produces a black discoloration of the nails, whereas the latter is white and produces a white discoloration.2 If suspected, the laboratory should be alerted as growth of this fungus is suppressed in a medium containing antibiotics which is usually used to grow dermatophytes.2 No simple effective oral or topical therapy has ever been reported for either Scytalidium species.3 A partially successful response to nail avulsion and topical ciclopiroxolamine cream has been reported for S. dimidiatum.4 We report the first case of successful treatment of S. hyalinum onychomycosis with twice daily topical 5% amorolfine nail lacquer (Loceryl®). A 62‐year‐old West Indian man, resident in the U.K. for 35 years, having last visited Jamaica in 1972, presented with a 20‐year history of an asymptomatic altered appearance to his finger nails. He was otherwise well, on no medication, and had not received any antifungal preparations from his family practitioner. On examination, he had lifting of the nail plate at the lateral and distal borders of six finger nails. The visible nail plates were virtually all white and opaque. There was no nail plate thickening and no scaling or erythema over the fingers or palms. The toe nails were unaffected. Nail clippings and subungual scrapings from the borders of the affected nails confirmed S. hyalinum on microscopy and cycloheximide‐free agar mycological culture. No other mycoses were found. He was asked to use 5% amorolfine nail lacquer on the affected nails twice a week, but inadvertently used the treatment twice a day without irritation to the fingers. Review at 8 weeks showed a marked improvement of the nails with little or no onycholysis, and normal nails proximally. Amorolfine was discontinued and a review 3 months later showed no recurrence. Amorolfine is a topical antifungal agent of the morpholine class. It diffuses through the nail with small amounts reaching the subungual surface.5 What percentage of drug is keratin‐bound, or free and active within the nail, is not known. Both S. dimidiatumand S. hyalinum have a 10‐fold higher minimal inhibitory concentration compared with dermatophytes when exposed in culture to either amorolfine or terbinafine.6 Oral terbinafine is known to be an ineffective treatment for Scytalidium spp. but is very successful against dermatophytes.3 Much higher concentrations of either drug may be required to deliver an effective fungicidal dose to treat Scytalidium spp. The twice daily use of topical 5% amorolfine may have provided the correct therapeutic dose. This is the first clinical report to show that amorolfine is an effective treatment for S. hyalinum.