Bardet-Biedl syndrome in two sibling pairs: a case series.

backgroundBardet-Biedl syndrome is a rare multisystem ciliopathy defined by retinal dystrophy, obesity, polydactyly, hypogonadism, and renal anomalies, often accompanied by neurodevelopmental and behavioral issues. Diagnosis relies heavily on clinical features, particularly in resource-limited settings where genetic testing is unavailable. CASE PRESENTATION: We describe two sibling pairs, all of South Asian, Pakistani ethnicity, clinically diagnosed with Bardet-Biedl syndrome using contemporary diagnostic frameworks. The first pair, two male brothers aged 17 and 21 years, came from a consanguineous family. The 17-year-old male presented with edema, polyuria and polydipsia, progressive night blindness, morbid obesity, polydactyly, hypogonadism, and retinopathy. Further investigations revealed renal impairment, and he was classified as definite Bardet-Biedl syndrome. His 21-year-old male brother had longstanding weight gain, striking polydactyly of the hands and feet, hypertension, moon facies, micropenis with gynecomastia, obesity, and behavioral disturbances including aggression and social withdrawal, along with nyctalopia and reduced visual acuity. His renal function was normal, and he was categorized as probable-to-definite Bardet-Biedl syndrome. The second pair, a 9-year-old male brother and a 4.5-year-old female sister, belonged to a nonconsanguineous Pakistani family. The brother exhibited decreased vision from early childhood, recurrent chest infections, urinary frequency, obesity with acanthosis, left-sided hand and foot polydactyly, micropenis, speech delay, and learning difficulties. Ultrasound findings showed normal kidneys and laboratory tests were within range, and he was considered definite Bardet-Biedl syndrome. His 4.5-year-old female sister presented with rapid weight gain, polyphagia, nyctalopia, reduced vision, behavioral dysregulation including hyperactivity, social and language delay, urinary frequency with enuresis, and microscopic hematuria on urinalysis despite normal renal size. She was categorized as probable Bardet-Biedl syndrome.

conclusionThis series highlights the significant intrafamilial variability of Bardet-Biedl syndrome and underscores the value of systematic clinical frameworks for early diagnosis and multidisciplinary management in settings where genetic confirmation is not available.