Costello syndrome in two siblings and minor manifestations in their mother. Further evidence for autosomal dominant inheritance?

We report on two siblings: the index patient, a 9 months old boy and his 2.5 years old sister, both presenting the main clinical signs and symptoms of Costello syndrome (CS): severe mental and motor retardation, feeding difficulties, failure to thrive in the first months of life, coarse facial appearance, skin hyperlaxity and skeletal deformities. Their mother presented with mild to moderate mental retardation, short stature, facial fullness and wart-like lesions on her face. The present observation confirms previous data on the apparent autosomal dominant pattern of inheritance in Costello syndrome with variable expression.