An X-linked dominant mutation in LAMP2 causing Danon disease associated with myotonia expanding the spectrum

Abstract

We describe a family with strong family history of cardiomyopathy. The mother has dilated cardiomyopathy with symptoms onset around 40 years old requiring treatment for both heart failure and atrial fibrillation. She does not have muscle weakness and her creatine kinase level was normal. The elder son has hypertrophic cardiomyopathy with symptoms onset at 20 years old, a mildly elevated creatine kinase of 1000 U/L but no muscle weakness. The younger brother with limited intelligence was asymptomatic all along. At the age of 15 with an incidental finding of raised serum transaminase levels he was referred for further investigations. Initial consultation confirmed mild proximal weakness, calves hypertrophy, creatine kinase up to 3500 U/L and echocardiogram ...