Abstract
A cross-sectional study of 41 children aged 4-17 years with alopecia areata and 41 of their siblings without alopecia areata was conducted. A total of 51% had the Severity of Alopecia Tool scores in the range of 0-25%, 12% had scores between 26% and 49%, and 36% had scores between 75% and 100%. The fecal microbiome was characterized using shotgun metagenomic sequencing. A comparison of alpha and beta diversity yielded a small but statistically significant difference on the basis of Jaccard distance, which measures species presence and absence between samples. However, a follow-up analysis did not reveal the particular species that were present more often in one group. The relative abundance of one species, Ruminococcus bicirculans, was decreased in patients with alopecia areata relative to that in their sibling controls. An analysis of gene ortholog abundance identified 20 orthologs that were different between groups, including spore germination genes and genes for metal transportation. The associations reported in this study support a view of pediatric alopecia areata as a systemic disease that has effects on hair but also leads to internal changes, including differences in the gut microbiome.