Previously reported 24 yrs. old male with history of WPW syndrome treated with radio frequency (RF) ablation 3 years ago, with progressive muscle weakness, mental retardation . Late gadolinium enhancement images in short axis and 4 chamber orientation showed a subendocardial pattern of enhancement in the lateral wall, papillary muscle and RV inferior junction point. Perfusion deficits and late enhancement patterns were atypical for sarcomeric hypertrophic cardiomyopathy. The LGE pattern were similar to the patient in this case report. Based on CMR findings Danon disease was suspected. LAMP 2 protein deficiency was confirmed on immunofluorescence study of skeletal muscle which supported the diagnosis of Danon disease.