Smith-Magenis Syndrome

Synonyms

SMS; del(17)p11.2; del(17)(p11.2p11.2); RAI1 mutation

Definition and Characteristics

Smith-Magenis syndrome is a complex neurobehavioral disorder that includes mild to moderate mental retardation, sleep disturbance due to inverted circadian rhythm of melatonin, infantile hypotonia and feeding difficulties. Craniofacial and skeletal abnormalities are common, including brachycephaly, broad nasal bridge, flat midface, tented upper lip, synophrys, hypertelorism, abnormally shaped or low-set ears, and brachydactyly. Hearing loss (both conductive and sensorineural), speech delay (expressive language >> receptive language), motor delay, and hypercholesterolemia are also common. Eye findings include myopia, strabismus, microcornea, nystagmus, cataracts, retinal detachment, and iris anomalies. With age, prognathism, scoliosis, and a hoarse, deep voice become more apparent [1]. Other features include cardiac defects (ventricular septal defect, atrial septal defect, aortic stenosis,...