Familial absorptive hypercalciuria and renal tubular acidosis.

Hypercalciuria was considered as a secondary condition when associated with familial renal tubular acidosis. Later studies suggested that hypercalciuria could lead to renal tubular acidosis and nephrocalcinosis. Selected members of a family spanning five generations were studied. Renal tubular acidosis was present in eight subjects in three consecutive generations. Increased 24-hour urinary calcium excretion was present in nine subjects in three consecutive generations, alone in the younger generation, and in combination with renal tubular acidosis and nephrocalcinosis in the older generation. Calcium loading tests showed the absorptive nature of hypercalciuria in nine of 18 subjects studied. This report suggests that in this family the absorptive hypercalciuria is an autosomal dominant genetic defect with complete penetrance and variable expressivity which leads to renal tubular acidosis and nephrocalcinosis.