Most patients with Smith-Magenis syndrome (SMS) have a deletion of ~4Mb at 17p11.2. All deletions associated with SMS involve the RAI1 gene. The majority of SMS features appear to be due to haploinsufficiency for RAI1. Some FISH probes do not include the RAI1 gene; in such comparisons, MLPA would be a more sensitive test for SMS. This laboratory performs deletion/duplication by MLPA of this region.