A boy presented at age 2.5 years with mild left ventricular hypertrophy and mi ld myopathy. Hypertrophic cardiomyopathy progressed relentlessly, leading to dea th at age 16 years shortly before planned heart transplantation. During the cour se of the disease, his mother developed severe dilated cardiomyopathy and died o f its complications at 46 years of age. The combination of myopathy and cardiomy opathy, the biochemical and electron microscopy findings in a muscle biopsy, and the pedigree suggested Danon disease (MIM 300257), an X-linked lysosomal stora ge disorder caused by deficiency of lysosome associated membrane protein-2 (LAM P2). The diagnosis was confirmed by the identification of a novel mutation, G138 A, in the LAMP2gene, leading to the premature stop codon W46X. Conclusion:Early diagnosis of Danon disease is important for genetic counselling and timely cardi ac transplantation, the only effective therapeutic option.
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