King syndrome: a genetically heterogenous phenotype due to congenital myopathies.

We report on a patient with myopathy, kyphoscoliosis, joint contractures, and a facial appearance consistent with King syndrome. Unlike other reported cases, our patient had hyperextensible joints, normal stature, and pectus excavatum. The cardiac ventricles, aorta, and pulmonary artery were dilated. Malignant hyperthermia did not occur under anaesthesia although there was a transient increase in CK levels. Muscle bulk and tone were significantly decreased but collagen and elastin fibres were normal. The variable clinical presentation of King syndrome suggests that the manifestations are caused by different congenital myopathies and in all cases there is probably an increased risk of malignant hyperthermia.