Progressive heart valve thickening and shrinkage, and progressive muscle cramps have not been reported as manifestations of glycogenosis type VII (Tarui's disease). In a 72-year-old female, Tarui's disease was diagnosed in 1997, initially manifesting as simple partial seizures since 1977, anginal chest pain since 1982 and muscle cramps since 1983. During the following years, low voltage ECG, ectopic supraventricular tachycardia, thickening of the mitral valve, mitral valve insufficiency, enlarged left atrium, left ventricular hypertrophy and diastolic dysfunction also developed. Neurological manifestations progressed to complex partial seizures, double vision, reduced tendon reflexes, central facial palsy, bradydiadochokinesia, distal weakness of the upper extremities and worsening muscle cramps. Thickening and shrinkage of the heart valves had further increased at 72 years of age. Progression of Tarui's disease may manifest as progressive thickening of the heart valves due to glycogen storage. Valve thickening may consecutively lead to valve insufficiency, enlargement of the atrium and atrial fibrillation. Progression of neurological manifestations may manifest as worsening muscle cramps.