Moreno-Arrones OM, Serrano-Villar S, Perez-Brocal V, et al. - This cross-sectional study was undertaken to determine if patients affected by alopecia universalis (n = 15) present differences in gut bacteria composition vs healthy controls (n = 15) and examine possible bacterial biomarkers of the disease. By sequencing the 16SrRNA of stool samples, gut microbiome of the study individuals was analyzed. A total of 30 study individuals (46.6% female; mean [SD] age, 40.1 [9.8] years) were enlisted. According to this cross-sectional study, neither alpha or beta diversity of gut microbiota displayed statistically significant differences between cases and controls. Alopecia universalis does not appear to have a broad influence on gut microbiota structure. Bacterial biomarkers found to be associated with the disease (Holdemania filiformis, Erysipelotrichacea, Lachnospiraceae, Parabacteroides johnsonii, Eggerthellaceae, Clostridiales vadin BB60 group, Bacteroides eggerthii and Parabacteroides distasonis) should be further examined as they may be involved in their pathophysiology or used as diagnostic instruments.