Prevalence of skin fungi markedly declines in the lesions of two patients with moderate hidradenitis suppurativa.

Hidradenitis suppurativa (HS) is a chronic inflammatory disorder affecting hair follicles in intertriginous regions, leading to painful nodules, sinus tracts, and scarring. The pathogenesis of HS is far from clear, but alterations in the bacterial community of the skin microbiome has been debated, yet the potential involvement of fungi - the mycobiome - has received almost no attention. Large areas of skin were sampled for amplicon metagenomics sequencing to negate the inference of low-sequence counts with the objective of examining the provenance of fungi between lesion and lesion-free skin from the same individuals. The DNA from skin swabs was isolated and the V4 region of the 18S rRNA gene was amplified and sequenced. Total fungal counts were inferred from taxonomic assignment of unique operational taxonomic units and absolute numbers then compared between skin sites. There were dramatically lower numbers of fungi in HS lesions with Malassezia dominance, as expected, across samples. This finding suggested, for the first time, that fungal depletion in lesions might be linked to HS pathology through disruption of normal skin barrier function and immunity, potentially due to reduced sebum production essential for fungal growth.