The presenting pt is a 13 years old girl who developed ESRD due to Bardet - biedl syndrome. She was complaining of sever weakness, lethargy, nausea, vomiting, dyspnea and decreased level of consciousness. Physical examination revealed all sings of this syndrome, which includes polydactyly, pigmented Retinopathy, truncal obesity, mental retardation, underdevelopment of sexual characteristics. In lab, sever anemia, serum creatinin 8mg/d, hyperkalemia and metobolic acidosis revealed. According to above mentioned evidences, and small size kidneys in ultrasonograghy, and also with attention to this point that she is a product of a familial marriage, diagnosis of Bardet - Biedl syndrome is documented.