The Association between Alopecia and Inflammatory Bowel Disease: A Systematic Review and Meta-Analysis.

IMPORTANCE The link between autoimmune gut disorders and different types of hair loss conditions has been recently investigated with an increased interest. With acknowledgement of the connection between immune dysregulation and the gut microbiome, this pathway is now becoming recognized as playing an important role in hair growth. The inflammatory cascade that results from the disruption of gut integrity such as seen in inflammatory bowel diseases (IBD) has been associated with certain types of alopecia. OBJECTIVE The aim of this work was to evaluate the association between alopecia and IBD. EVIDENCE REVIEW A primary literature search was conducted using the PubMed, Embase, and Web of Science databases to identify articles on co-occurring alopecia and IBD from 1967 to 2020. A total of 79 studies were included in the review. A one-way proportional meta-analysis was performed on 19 of the studies to generate the pooled prevalence of alopecia and IBD. FINDING The pooled prevalence of non-scarring alopecia among IBD patients was 1.12% (k = 7, I2 = 98.6%, 95% CI 3.1-39.9); the prevalence of IBD among scarring and non-scarring alopecia was 1.99% (k = 12; I2 = 99%, 95% CI 6.2-34). The prevalence of non-scarring alopecia areata (AA) among IBD was compared to the prevalence of AA in the general population (0.63 vs. 0.1%; p < 0.0001). Similarly, the prevalence of IBD among the scarring and non-scarring alopecia groups was compared to the prevalence of IBD in the general population (1.99 vs. 0.396%; p = 0.0004). CONCLUSION IBD and alopecia, particularly AA, appear to be strongly associated. Dermatology patients with alopecia may benefit from screening for IBD.