Familial patterns of alopecia areata: A systematic review and meta-analysis

Background: Alopecia Areata (AA) is a T cell-mediated autoimmune disease characterized by sudden hair loss. It is associated with a significant familial predisposition and comorbidities such as thyroid disease, diabetes, atopic dermatitis, and vitiligo. This study aims to systematically review and meta-analyze the prevalence of familial AA and its associated comorbidities to better understand the hereditary nature of the disease. Methods: A systematic review and meta-analysis were conducted following the PRISMA guidelines. Relevant studies were identified from databases including EMBASE, Cochrane Library, PubMed, and Web of Science up to October 15, 2023. Studies were included if they reported on AA patients with a confirmed diagnosis and a family history of AA or related comorbidities. Data extraction and quality assessment were performed by two independent reviewers, with discrepancies resolved by a third reviewer. Pooled prevalence estimates were calculated using a random effects model. Results: The meta-analysis included 67 studies, encompassing 24,226 AA patients and their relatives. The prevalence of a family history of alopecia areata (AA) was found to be 17.6 %, indicating that 17.6 % of individuals with AA have a positive family history of the condition. (CI: 14.9 %-20.6 %, I2 = 96 %). The prevalence among relatives was 0.90 % (CI: 0.55 %-1.47 %, I2 = 98 %), with the highest prevalence observed in first-degree relatives at 3.22 % (CI: 2.31 %-4.48 %, I2 = 94 %). Comorbid conditions were present in 9.61 % (CI: 6.98 %- 13.1 %, I2 = 95 %) of family members across first-, second-, and third-degree relatives of individuals with alopecia areata have comorbid autoimmune or related conditions, including thyroid disease (4.7 %), diabetes (10.1 %), atopic dermatitis (18.9 %), vitiligo (5.5 %), and other autoimmune disease (12.1 %). Conclusion: This systematic review and meta-analysis highlight the significant familial risk and comorbidities in family members of AA patients. The findings emphasize the need for comprehensive family monitoring, which includes regular health screenings for autoimmune and related conditions among relatives of AA patients, and genetic counseling to educate families on hereditary risks and to guide early intervention and monitoring strategies. It can lead to improved outcomes. In the future, large population-based studies focusing on second and third-degree relatives are needed to further elucidate these associations.