Autoimmune pernicious anemia in clinically diagnosed Bardet–Biedl syndrome: a case report and brief literature review

Bardet–Biedl syndrome is a rare autosomal recessive ciliopathy that may be diagnosed clinically in resource-limited settings where molecular testing is unavailable. Autoimmune pernicious anemia has been rarely described in association with BBS, and its relationship to BBS-related immune dysregulation remains uncertain. We report an 18-year-old Pakistani woman of Pashtun ethnicity from a consanguineous family who presented with four months of progressive fatigue, weakness, pallor, and exertional dyspnea. Evaluation revealed severe macrocytic anemia due to vitamin B12 deficiency, with positive anti-intrinsic factor and anti-parietal cell antibodies confirming autoimmune pernicious anemia. Further history identified childhood-onset retinal dystrophy progressing to blindness, postaxial polydactyly, developmental delay, primary amenorrhea, bilaterally small kidneys, diabetes mellitus, parental consanguinity, and a similarly affected sibling. She fulfilled all six major and two minor clinical diagnostic criteria for Bardet–Biedl syndrome; molecular confirmation could not be arranged because of resource limitations. She improved after packed red cell transfusion and intramuscular cyanocobalamin and was discharged on lifelong vitamin B12 replacement. This case documents a rare co-occurrence of autoimmune pernicious anemia in a patient clinically fulfilling all major criteria for Bardet–Biedl syndrome in a resource-limited setting where molecular confirmation was unavailable. While a single clinical case cannot establish causality or exclude overlapping conditions, the observation is biologically plausible in light of emerging evidence linking ciliary dysfunction to immune dysregulation. Clinicians managing patients with suspected or confirmed BBS should maintain vigilance for autoimmune pernicious anemia when evaluating unexplained macrocytic anemia or vitamin B12 deficiency.