BH05: Nondermatophyte onychomycosis and paronychia secondary to Aspergillus niger

T. Chohan, N. Heysa and A. Ilchyshyn

University Hospital Coventry and Warwickshire, Coventry, UK

Aspergillus spp. are emerging causative agents of nondermatophyte mould (NDM), with a worldwide increasing incidence. The infections are difficult to diagnose given that they are common nail colonizers and contaminants of mycology laboratories. In 2012, a systematic review proposed six major diagnostic criteria: (i) identification of the NDM in the nail by microscopy; (ii) isolation in culture; (iii) repeated isolation in culture; (iv) inoculum counting; (v) failure to isolate a dermatophyte in culture; and (vi) identification on histology (Gupta AK, Drummond-Main C, Cooper EA et al. Systematic review of nondermatophyte mold onychomycosis: diagnosis, clinical types, epidemiology, and treatment. J Am Acad Dermatol 2012; 66: AB122). Gupta et al. recommended using three or more of these criteria in order to rule out contamination. A 59-year-old man presented with pain, onycholysis and a black discolouration of the proximal and medial nail plate on the left great toe. The corresponding nailfolds were erythematous, indurated, fluctuant and tender. He was otherwise fit and well, and had been treated for dermatophyte onychomycosis affecting the same toe a year previously. The nail plate was mechanically avulsed, revealing a yellowish exudate that was swabbed, which showed heavy growth of Aspergillus niger. Nail plate culture showed a mixed growth of nondermatophyte fungi. Histopathological analysis of the nailbed demonstrated fungal hyphae with no evidence of malignancy. The patient was started on oral voriconazole 400 mg loading dose on day 1, and 200 mg twice daily thereafter for 2 months. After 1 month, there was a marked reduction in pain and inflammation of the nailfold. Aspergillus species account for around 0·5–3% of all cases of onychomycosis. Its prevalence varies considerably with geographical location, and predisposing factors range from the presence of nail trauma and diabetes to socioeconomic factors like poor hygiene and deprivation. Given that our patient had previous dermatophyte onychomycosis, it is likely that the A. niger initially opportunistically colonized a dystrophic nail plate before causing clinical infection. It often presents as a milky white and black discolouration, and tends to produce a proximal subungual onychomycosis with nailfold pain and inflammation. Oral terbinafine or itraconazole are commonly used and effective at treating Aspergillus spp. but not other NDMs (Tosti A, Piraccini BM, Lorenzi S. Onychomycosis caused by nondermatophytic molds: clinical features and response to treatment of 59 cases. J Am Acad Dermatol 2000; 42: 217–24). We chose to treat with voriconazole on advice from our local microbiology department. We present a case of NDM onychomycosis secondary to A. niger, over a year after dermatophyte onychomycosis was treated on the same digit.