Publication:

Genotype–phenotype discordance in Noonan syndrome: prenatal diagnosis in an asymptomatic mother

Noonan syndrome is a RASopathy with variable clinical expression. Prenatal suspicion is often based on ultrasound findings such as increased nuchal fold. Increased nuchal fold on prenatal ultrasound led to genetic evaluation and identification of a pathogenic MAPK1 variant in the foetus. Segregation analysis revealed the same mutation in the phenotypically normal mother also. The neonate after birth was clinically normal with no structural abnormalities. This case highlights the importance of prenatal markers and demonstrates that Noonan syndrome may be present without classical phenotypic features.