Marfan syndrome is an autosomal dominant condition, with manifestations mainly 
in the skeletal, ocular, and cardiovascular systems. The disorder is caused by 
mutations in fibrillin-1 gene (FBN1). The majority of these are family-specific 
point mutations, with a small number being predicted to cause exon-skipping. To 
date, there have only been five reports of in-frame exon deletions in FBN1, with 
the largest of these spanning three exons. Mosaicism is rarely recorded and has 
only been reported in the unaffected, or mildly affected, parents of probands. 
Here, we report on the clinical histories of two children with exon deletions in 
FBN1. Both have severe Marfan syndrome with significant signs in infancy. One 
patient has a deletion of exon 33, which has not previously been reported. The 
other has the largest reported deletion, which spans 37 exons, and also 
represents the first reported case of mosaicism in a patient with Marfan 
syndrome.