Cap myopathy is a very rare congenital myopathy presenting a weakness of facial and respiratory muscles associated with craniofacial and thoracic deformities, as well as weakness of limb proximal and distal muscles. Onset is at birth or in childhood, weakness progression is slow but may lead to a severe and even fatal prognosis. The disease is MONDO_0015753 (cap myopathy). Also known as: Cap disease.