Laboratory diagnosis and prevalence of onychomycosis caused by Fusarium and Scytalidium species

Introduction: Scytalidium and Fusarium are opportunistic saprophytic fungi commonly found in subtropical areas, being responsible for several cases of onychomycoses caused by non-dermatophytic filamentous fungi in these regions. The aim of this study is to determine the prevalence of onychomycoses caused by these pathogens, which population and site of infection are most affected, and which morphological characteristics should be considered for the culture method. Methods: A 5-year retrospective analysis was performed with data collected from mycological examinations at a clinical analysis laboratory located in Porto Alegre, Rio Grande do Sul, Brazil. Results: Of the 2479 cases of onychomycosis studied, Scytalidium and Fusarium had a prevalence of 3% and 7%, respectively. About 57% of these infections affected women aged 30-69 years. In 78% of the cases of onychomycosis, toenails were affected. Positive reports of Scytalidium spp. exhibited chain-shaped arthroconidia, while Fusarium spp., fusiform, elongated or canoe-shaped macroconidia, and elongated ovoid microconidia were observed. Conclusion: This retrospective study revealed that Fusarium spp. has a higher prevalence than Scytalidium spp. The feet are the most affected body region. Elderly women are the most affected population by these fungi. For diagnosis, the main findings of Scytalidium spp. and Fusarium spp. are the cylindrical chain arthroconidia and the canoe-shaped, fusiform, or half-moon-shaped macroconidia, respectively.