An attenuated phenotype of Costello syndrome in three unrelated individuals with a HRAS c.179G>A (p.Gly60Asp) mutation correlates with uncommon functional consequences

Heterozygous germline mutations in the proto‐oncogene HRAS cause Costello syndrome (CS), an intellectual disability condition with severe failure to thrive, cardiac abnormalities, predisposition to tumors, and neurologic abnormalities. More than 80% of patients share the HRAS mutation c.34G>A (p.Gly12Ser) associated with the typical, relatively homogeneous phenotype. Rarer mutations occurred in individuals with an attenuated phenotype and...