Adult muscle phosphorylase "b" kinase deficiency.

A 35-year-old man had severe exercise intolerance and cramps. Venous blood lactate did not rise after ischemic exercise, and electromyographically silent contracture of hand muscles appeared. Histochemistry and electronmicroscopy of a muscle biopsy revealed subsarcolemmal and intermyofibrillar accumulation of glycogen. Biochemical studies showed moderately increased amount of glycogen. Total phosphorylase activity was normal, but the active form "a" was 27% of normal. Phosphorylase kinase activity was 12% of the normal value and was normal in leukocytes and erythrocytes.