Mutations in the gene for fibrillin-1 (FBN1) cause Marfan syndrome, an autosomal 
dominant disorder of connective tissue with prominent manifestations in the 
skeletal, ocular, and cardiovascular system. There is a remarkable degree of 
clinical variability both within and between families with Marfan syndrome as 
well as in individuals with related disorders of connective tissue caused by 
FBN1 mutations and collectively termed type-1 fibrillinopathies. The so-called 
neonatal region in FBN1 exons 24-32 comprises one of the few generally accepted 
genotype-phenotype correlations described to date. In this work, we report 12 
FBN1 mutations identified by temperature-gradient gel electrophoresis screening 
of exons 24-40 in 127 individuals with Marfan syndrome or related disorders. The 
data reported here, together with other published reports, document a 
significant clustering of mutations in exons 24-32. Although all reported 
mutations associated with neonatal Marfan syndrome and the majority of point 
mutations associated with atypically severe presentations have been found in 
exons 24-32, mutations associated with classic Marfan syndrome occur in this 
region as well. It is not possible to predict whether a given mutation in exons 
24-32 will be associated with classic, atypically severe, or neonatal Marfan 
syndrome.