Renal tubular acidosis I distal type (dRTA I) is a rare autosomal dominant disorder with a primary defect of urinary acidification. Clinical symptoms are variable and include growth retardation, rickets and nephrocalcino- sis. Laboratory findings include metabolic acidosis, fixed specific gravidity of urine (1004 - 1010), fixed urinary pH of about 5.0, increased serum chloride, low serum bicarbonate, hypocalcaemia. Authors present data on the familial occurrence this disorder in a severely affected daughter and her mildly affected father. The diagnosis was confirmed by detection of mutation in the anion exchanger 1 (AE1) gene in both the father and the daughter. DNA analysis can be used for postnatal as well as prenatal detection of this treatable disorder.

        Key words: autosomal dominant inheritance, renal tubular acidosis type I, defect of distal tubule, nephrocal- cinosis, anion exchanger 1 gene (AE1) mutation responsible for dRTA