Phenotypic Heterogeneity in Familial Takayasu Arteritis Across Two Families: A Case-Based Review.

Background: Takayasu arteritis (TAK) is a rare large-vessel vasculitis that predominantly affects young women. Familial cases are uncommon but suggest a possible genetic predisposition. Case Report: We describe five familial TAK cases from two families. In the first, two sisters had distinct disease patterns: one with severe supra-aortic involvement (Hata IIa), requiring intensive immunosuppression and vascular interventions; the other with isolated abdominal aortic disease (Hata IV), successfully managed with standard therapy. In the second family, three siblings presented with varying severity. One sister had mild disease responsive to therapy, whereas another developed rapidly progressive TAK with multivessel involvement, necessitating complex surgical management and ultimately succumbing to COVID-19 complications. Their brother presented with extensive Hata V involvement and achieved remission following brief medical therapy. Conclusion: Familial TAK demonstrates marked clinical and radiological heterogeneity, even among first-degree relatives. These findings underscore the importance of clinical vigilance and prompt evaluation for relatives who develop suggestive symptoms, to enable timely diagnosis and improve clinical outcomes.