Emergomycosis – the global rise of a new dimorphic and systemic mycosis: current trends and future perspectives
Emergomycosis is a systemic fungal disease caused by thermally dimorphic fungus Emergomyces spp., so named because of its recent global emergence. It was formerly classified under genus Emmonsia but a taxonomic revision based on ribosomal DNA sequences, using concatenated sequence data of the loci LSU, ITS, TUB2, TEF3, and RPB2, have placed all Emmonsia-like fungi under a separate genus Emergomyces. The genus contains Emergomyces pasteurianus (most widespread) as the type species and other species: Es. africanus, Es. canadensis, Es. orientalis, and Es. europaeus. Whole genome sequencing data show that both Es. africanus and Es. pasteurianus contain the alpha mating-type locus (MAT1-1).
The disease classically manifests in disseminated form with extensive cutaneous involvement, usually in immunodeficienct patients. So far, only a few sporadic cases have been reported from Asia, Europe, Africa and North America. But considering the overwhelming population of immunocompromised patients, it is presumed that the disease must be having a worldwide distribution with many cases going undetected. Emergomycosis should be considered in the differential diagnosis of histoplasmosis as there is considerable clinical and histopathological overlap between the two diseases. Internal transcribed spacer (ITS) sequencing of ribosomal DNA is the gold standard for identification but its application is jeopardised in resource limited settings. Therefore, the development of an affordable, accessible, and feasible diagnostic test should be prioritized to enable the diagnosis in endemic regions and also for epidemiological surveillance. There are limited studies on antifungal susceptibility profile of Emergomyces, no existing clinical breakpoints, and no consensus treatment guidelines. This presentation addresses taxonomic, clinical, diagnostic, and therapeutic aspects of emergomycosis worldwide. It also highlights the potential areas of future studies that may open up new therapeutic approaches for better patient management and improved outcomes. More research is warranted to understand the geographic range, ecology, epidemiology and immunopathogenesis of this mycoses, to understand the full clinical spectrum of disease and to optimize clinical diagnostic, therapeutic efficacies and overall patient management.