Purpose: We determined the mode of inheritance of idiopathic hypercalciuria and its subtypes.
Materials and methods: We evaluated 40 children with symptomatic idiopathic hypercalciuria and 129 of their first-degree relatives (80 parents and 49 siblings). In hypercalciuric individuals in families with at least 2 affected members the type of idiopathic hypercalciuria was determined by the calcium loading test.
Results: Of the 40 affected children 19 (47.5%) had 1 or more affected first-degree relatives (23 of 80 parents and 2 of 49 siblings). In all 44 affected members of the 19 hypercalciuric families (19 index cases, 23 parents and 2 siblings) the type of idiopathic hypercalciuria was determined (absorptive in 38 and renal in 6). Study of the pedigree of the 19 families showed that idiopathic hypercalciuria appears to be transmitted as an autosomal dominant trait. With only 1 exception the subtype of disease was specific for members of the same family.
Conclusions: Idiopathic hypercalciuria has a familial or sporadic pattern. In the familial pattern an autosomal dominant inheritance is present. The type of the disease is identical in affected members of the same family. The absorptive subtype is more frequent.