We report the case of a term infant with cystic hygroma revealed by fetal u
ltrasound scanning and characteristic craniofacial dysmorphism at birth, co
mpatible with a clinical picture of Noonan syndrome. The infant had a signi
ficant factor XII deficiency, found also in his parents. In the following m
onths, a worsening of cardiorespiratory function, due to a rapidly progress
ive hypertrophic cardiomyopathy, occurred, causing the death of the infant.