The Marshall-Smith syndrome is a malformation syndrome characterized by accelerated skeletal maturation, relative failure to thrive, respiratory difficulties, mental retardation, and unusual facies, including prominent forehead, shallow orbits, blue sclerae, depressed nasal bridge, and micrognathia.
The primary clinical features of this syndrome are moderate to severe developmental delay with absent or limited speech, unusual behavior such as playing in a repetitive or stereotypic manner with a favorite toy, dysharmonic bone maturation, respiratory compromise secondary to upper airway obstruction, short stature, and kyphoscoliosis. Characteristic facial features included high forehead, underdeveloped midface, proptosis, anteverted nares, and everted lips. Minor abnormalities of brain morphology such as hypoplasia of the corpus callosum were common.