The Coffin-Siris syndrome: five new cases including two siblings.

Five new cases and one previously reported case of the Coffin-Siris syndrome are described. These cases plus the remaining four already published bring to ten the number of cases available for scrutiny. Constant features (100% frequency) include variable degrees of mental retardation, nail hypoplasia or absence with predominantly fifth digit involvement, hypotonia, infancy feeding problems, and retarded bone age. Frequent features (75% to 90%) include postnatal growth deficiency, microcephaly, wide nasal tip and mouth, prominent lips, eyebrow/eyelash hypertrichosis, and scalp hair hypotrichosis. Significant but less frequent findings include short philtrum (50%, scoliosis (40%), decreased fetal activity (40%), smallness for gestational age (30%), and congenital heart defects (30%). We found the craniofacial phenotype to be mild in the young infant, but progressively more characteristic with age. Autosomal recessive inheritance is suspected on the basis of our brother-and-sister pair.