Clinical and histological aspects of toenail onychomycosis caused by Aspergillus spp.: 34 cases treated with weekly intermittent terbinafine

Abstract

Background: Non-dermatophytic onychomycoses represent 1.45-17.6% of all fungal nail infections. Epidemiological studies have shown that Aspergillus spp. are emerging fungal agents of toenail onychomycosis. Indeed, after Scopulariopsis spp. the genus Aspergillus is the second most common agent of non-dermatophytic onychomycosis. The diagnosis and treatment of toenail onychomycosis caused by non-dermatophyte moulds are not always straightforward.

Objectives: The aims of this study were to describe the clinical appearance of toenail onychomycosis due to Aspergillus spp., to investigate the pathogenetic role of these agents and to evaluate the efficacy and safety of weekly intermittent terbinafine (500 mg/day for 1 week each month for 3 months) in the treatment of these patients.

Patients and methods: Mycological study of 2,154 patients with onychodystrophy revealed 1,228 onychomycoses (57%) including 71 cases due to non-dermatophytic fungi (5.6%). Non-dermatophytic onychomycosis caused by Aspergillus spp. represented 2.6% of all onychomycoses. The subjects were 34 patients (22 females, 12 males, age range 30-82 years) observed between September 1999 and December 2001, with toenail onychomycosis caused by Aspergillus spp. confirmed by standard techniques (microscopic examination and culture according to the criteria of English), histological examination of nail clippings and scanning electron microscope examination of the cultures whenever necessary.

Results: The clinical features suggesting onychomycosis due to Aspergillus spp. are chalky deep white nail, rapid involvement of lamina and painful perionyxis without pus. Standard mycological tests (direct microscopy and fungal culture) and histological examination confirmed the pathogenetic role of Aspergillus spp. in onychomycoses. In particular, the histological examination was positive in 28 cases (82%) and useful in identifying typical aspects of Aspergillus spp. nail infections. At the follow-up, 12 months after the start of therapy with pulsed terbinafine, clinical and mycological recovery was confirmed in 30 of the 34 patients (88%).

Conclusions: Treatment of non-dermatophytic onychomycosis with terbinafine usually requires at least 3 months of continuous systemic therapy. Our study of 34 patients confirms that terbinafine is particularly effective in the treatment of Aspergillus spp. nail infections and that a pulsed regimen is more economical and less demanding.