Abstract
In glycogen storage disease type III (GSD III), deficiency of the debranching enzyme causes storage of an intermediate glycogen molecule (limit dextrin) in the affected tissues. In subtype IIIa hepatic tissue, skeletal- and cardiac muscle tissue is affected, while in subtype IIIb only hepatic tissue is affected. Cardiac storage of limit dextrin causes a form of cardiomyopathy, which resembles primary hypertrophic cardiomyopathy on cardiac ultrasound. We present a 32-year-old GSD IIIa patient with severe left ventricular hypertrophy (LVH) first diagnosed at the age of 8 years. LVH remained stable and symptomless until the patient presented at age 25 years with increasing dyspnea, fatigue, obesity, and NYHA (New York Heart Association) functional classification two out of four. Dyspnea, fatigue, and obesity progressed, and at age 28 years she was severely symptomatic with NYHA classification 3+ out of 4. On echocardiogram and electrocardiogram, the LVH had progressed as well. Initially, she was rejected for cardiac transplantation because of severe obesity. Therefore, a 900 cal, high protein diet providing 37% of total energy was prescribed during 4 months on which 10 kg weight loss was achieved. However, her symptoms as well as the electrocardiographic and echocardiographic LVH indices had improved dramatically - ultimately deferring cardiac transplantation. Thereafter, the caloric intake was increased to 1,370 cal per day, and the high protein intake was continued providing 43% of total energy. After 3 years of follow-up, the patient remains satisfied with reasonable exercise tolerance and minor symptoms in daily life.