Spontaneous Posterior Dislocation of both Lenses in a Patient with Marfan’s Syndrome: 17 years Without Complications

Correlation between FBN1 mutations and ocular features with ectopia lentis in the setting of Marfan syndrome and related fibrillinopathies

Mutations of fibrillin-1 (FBN1) have been associated with Marfan syndrome and pleiotropic connective tissue disorders, collectively termed as "type I fibrillinopathy". However, few genotype-phenotype correlations are known in the ocular system. Patients with congenital ectopia lentis (EL) received panel-based next-generation sequencing, complemented with multiplex ligation-dependent probe amplification. In a total of 125 probands, the ocular phenotypes were compared for different types of FBN1 mutations. Premature termination codons were associated with less severe EL and a thinner central corneal thickness (CCT) than the inframe mutations. The eyes of patients with mutations in the C-terminal region had a higher incidence of posterior staphyloma than those in the middle and N-terminal regions. Mutations in the TGF-β-regulating sequence had larger horizontal corneal diameters (white-to-white [WTW]), higher incidence of posterior staphyloma, but less severe EL than those with mutations in other regions. Mutations in the neonatal region were associated with thinner CCT. Longer axial length (AL) was associated with mutations in the C-terminal region or TGF-β regulating sequence after adjusting for age, EL severity, and corneal curvature radius. FBN1 genotype-phenotype correlations were established for some ocular features, including EL severity, AL, WTW, CCT, and so forth, providing novel perspectives and directions for further mechanistic studies.

Severe Marfan syndrome due to FBN1 exon deletions

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.