Germline mosaicism of a novel mutation in lysosome-associated membrane protein-2 deficiency (Danon disease).

We identified a family with lysosome-associated membrane protein-2 deficiency (Danon disease) associated with a novel 883 ins-T mutation in the lysosome-associated membrane protein-2 gene located at Xq24. Although the affected son and daughter carried the same mutation, it was not detected in their mother's peripheral blood or buccal cells; this indicated germline mosaicism. This is the first molecular evidence for germline mosaicism in Danon disease and has important implications for genetic counseling.