Predominance of Fonsecaea nubica in Chromoblastomycosis: A Single-Centre Study from Southern India

Chromoblastomycosis is a neglected tropical disease caused by melanized fungi that predominantly affects agricultural workers in endemic areas. This single-centre study from Kerala, South India, identified Fonsecaea nubica as the predominant Fonsecaea species among cultured isolates.

We conducted a prospective study of 70 suspected cases in the state of Kerala, India, from November 2022 to May 2024. Sixteen cases were confirmed or probable based on predefined criteria. Molecular identity of isolates was confirmed using ITS and CDC42 gene sequencing. Clinical, histopathological, microbiological, treatment, and outcome data were prospectively collected over a one-year follow-up period.

Of the 16 confirmed or probable cases, nine isolates were cultured: six Fonsecaea isolates identified as F. nubica by CDC42 phylogeny (100% Fonsecaea isolates, 66.7% of cultured isolates) and three non-Fonsecaea isolates (Medicopsis romeroi, Cladosporium spp., and Lasiodiplodia spp.) identified by ITS/morphology. All cases originated from the Kottayam and Idukki districts, with 13/16 (81.3%) being male and 11/16 (68.8%) agricultural workers. Lesions predominantly affected the lower extremities (56.3%), with verrucous lesions being the most common (43.8%). All patients received itraconazole therapy, with 14/16 (87.5%) achieving clinical cure.

These findings underscore the importance of molecular diagnostics in accurately characterizing the epidemiology of chromoblastomycosis in endemic regions. The emergence of F. nubica has implications for its clinical management, diagnosis, and surveillance. The study contributes valuable data to the limited molecular epidemiological literature from India and supports ongoing efforts to improve chromoblastomycosis surveillance and management in resource-limited settings.