Features include facial malformations (microstomia, micrognathia,
retrognathia, blepharophimosis, short palpebral fissures, telecanthus, sad
“fixed” facies, low-set ears, short neck), and musculoskeletal signs (myopathy, myotonia,
muscular hypertrophy, restricted joint mobility, osteoporosis, dislocated
hip, delayed bone age, epiphyseal anomaly, kyphosis, scoliosis, pectus
carinatum, abnormal vertebral size/shape, anterior bowing of the long
bones). Mental retardation (20%) and areflexia/hyporeflexia are
described. Short stature, intrauterine growth retardation, myopia, cataract,
umbilical hernia, generalized hirsutism, feeding and swallowing
difficulties, and recurrent hyperthermia may be observed.