The neonatal Marfan syndrome is an autosomal dominantly inherited disease with 
an extremely poor prognosis. This report gives a clinical and echocardiographic 
description of an infant with a mutation in exon 29 of the fibrillin-1 gene 
(FBN1), a region in which this severe form of Marfan syndrome seems to cluster. 
The infant died at the age of 3 months due to severe acute mitral regurgitation 
leading to intractable heart failure.