Differential Diagnosis of RASopathies. Description of a Novel Variant Causing Cardiofaciocutaneous Syndrome

Cardiofaciocutaneous (CFC) syndrome is a rare RASopathy caused by RAS/MAPK pathway mutations, often overlapping clinically with Noonan and Costello syndromes, making molecular testing crucial for accurate diagnosis. We describe an infant with macrocephaly, hydrocephalus requiring shunt, axial hypotonia, hypertrophic cardiomyopathy, and mitral valve dysplasia. MRI showed ventriculomegaly and cerebellar tonsillar descent; echocardiography revealed concentric left ventricular hypertrophy. Genetic testing identified a de novo KRAS missense variant (p.Pro34Arg), a rare CFC cause (< 2% cases), not previously reported in our population. This case broadens the mutational spectrum of CFC and underscores molecular analysis for diagnosis, prognosis, and genetic counseling