Metagenomic profiling reveals dominance of gram‐positive bacteria in the gut microbiome shifts associated with immunoglobulin A vasculitis (Henoch–Schönlein Purpura)

OBJECTIVES: Immunoglobulin A vasculitis (IgAV), previously known as Henoch–Schönlein purpura, is the most common vasculitis that has a classical skin manifestation of palpable purpuric rash. Factors pertinent to IgAV remain inadequately understood. Here, we aimed to examine the gut microbiome shifts associated with IgAV and its recovery. METHODS: Stool samples were collected from 10 children with IgAV (6–14 years old) before and after a multi‐drug therapy, along with 9 age‐matched healthy children. The samples were subjected to metagenomic analyses to investigate the taxonomic and functional shifts of the gut microbiome. RESULTS: The analyses revealed that compared with healthy controls, treatment‐naïve patients exhibited substantial taxonomic and functional alterations of gut microbiota, including 104 IgAV‐depleted species and 7 IgAV‐elevated species (FDR < 0.05). After treatment, the IgAV patients displayed a partial restoration of the microbiota shifts, as the relative abundances of some biomarkers (e.g. 9 genera and 22 species) became comparable (FDR > 0.1) between the patients and healthy controls. The treatment‐responsive features included Weissella, Faecalibacterium prausnitzii and Bifidobacterium pseudocatenulatum and three components of a putative glutamine transport system. Importantly, gram‐positive bacteria accounted for over 85% of the numbers and total relative abundance of the species that were associated with IgAV and responsive to the treatment. In addition, of the 122 IgAV‐depleted bacterial genes, 82 were mainly contributed by gram‐positive bacteria and 12 by gram‐negative bacteria. CONCLUSIONS: Gram‐positive bacteria are the main drivers underlying the gut microbiome shifts of IgAV, which may assist rational management of the disease.