Fifteen of the patients with CK > 500 UI/L had a diagnosis: dystrophinopathies (N = 6), myositis (N = 5), gamma-sarcoglicanopathy (N = 1), carnitine palmitoyl transferase 2 deficiency (CPT2) (N = 1), non-classified myopathy (N = 1), and neuropathy (N = 1). The gene discussed is CPT2; the disease is hyperinsulinemic hypoglycemia, familial, 4.