Purpose of review: Recent clinical, neuroimaging, sleep, and molecular cytogenetic studies have provided new insights into the mechanisms leading to the Smith-Magenis phenotype and are summarized in this review.
Recent findings: Cross sectional studies of patients with Smith-Magenis syndrome have found evidence for central and peripheral nervous system abnormalities, neurobehavioral disturbances, and an inverted pattern of melatonin secretion leading to circadian rhythm disturbance. A common chromosome 17p11.2 deletion interval spanning approximately 3.5 Mb is identified in about 70% of individuals with chromosome deletion. Recently heterozygous point mutations in the RAI1 gene within the Smith-Magenis syndrome critical region have been reported in Smith-Magenis syndrome patients without detectable deletion by fluorescent in-situ hybridization. Patients with intragenic mutations in RAI1 as well as those with deletions share most but not all aspects of the phenotype.
Summary: Findings from molecular cytogenetic analysis suggest that other genes or genetic background may play a role in altering the functional availability of RAI1 for downstream effects. Further research into additional genes in the Smith-Magenis syndrome critical region will help define the role they play in modifying features or severity of the Smith-Magenis syndrome phenotype. More research is needed to translate advances in clinical research into new treatment options to address the sleep and neurobehavioral problems in this disorder.