Two novel mutations causing familial benign hypocalciuric hypercalcaemia in three Scottish families.

Background And Aims: Familial benign hypocalciuric hypercalcaemia (FBHH) is a benign autosomal dominantly inherited condition which results in elevated serum calcium and low urinary calcium. This condition is of clinical interest because it can be mistakenly diagnosed as primary hyperparathyroidism (PHP). In most cases FBHH can be shown to be due to a mutation in the calcium sensing receptor (CASR) gene and we aimed to find the causative mutation in three Scottish kindreds with FBHH.

Methods: We used a combination of denaturing gradient gel electrophoresis and direct DNA sequencing to detect mutations in the CASR gene.

Results: We detected a mutation in the CASR gene in each of the three kindreds. Two different mutations were detected (the same one was present in two kindreds). Neither mutation has been reported previously. All hypercalcaemic individuals from each kindred had the appropriate mutation while all normocalcaemic individuals did not.

Conclusion: In the vast majority of kindreds with FBHH which have been reported previously, the CASR mutation responsible is private to that kindred. In three Scottish kindreds we have identified two new mutations.