Reasons to suspect SMS:
(1) typical facies (flat face, tented upper lip, brachycephaly)
(2) sleep disturbance (early morning wakings, other)
(3) infantile hypotonia with feeding difficulties
(4) variable mental retardation
(5) developmental delay
(6) delays in speech and motor skills
(7) self-injurious and/or stereotypical behaviors
Genetic defects:
(1) 17p11.2 microdeletion
(2) retinoic acid-induced 1 (RAI1) mutation (inherited or de novo)
Differential diagnosis:
(1) Williams syndrome
(2) 22q11.2 deletion
(3) Sotos syndrome
(4) 9q34 deletion syndrome
(5) Prader-Willi syndrome
