Familial spontaneous pneumothorax is not linked to FBN-1, the defective gene in the Marfan syndrome

Background: Primary spontaneous pneumothorax (PSP) is common and associated with a tall thin body habitus similar to that of the Marfan syndrome. Its aetiology is unknown and most cases are isolated. A small proportion are familial, with 59 reported pedigrees, which are mostly autosomal dominant (as is Marfan syndrome), although X-linked inheritance cannot be excluded in some families. The Marfan syndrome sometimes causes emphysema and PSP and produces variable phenotypes. It is due to mutations in the fibrillin-1 (FBN-1) gene coding for glycoprotein, which polymerises to form microfibrils in the extracellular matrix of connective tissue. Given its similarities to Marfan syndrome, we hypothesized that familial PSP is also due to mutations in the FBN-1 gene. Methods: EDTA blood was obtained from both affected and unaffected family members of three pedigrees with PSP. In total, blood was obtained was 14 affected and 6 unaffected individuals. Pedigree examination confirmed autosomal dominant inheritance. Genomic DNA was extracted from blood and four microsatellite polymorphic markers located within the FBN-1 gene were amplified by PCR using fluorescentry labelled primers. Amplified PCR products were sized by automated fluorescence-based genotyping and FBN-1 haplotypes were assigned to each family member. Results: Overall, there was no linkage between FBN-1 and the disease phenotype. For two of the three families linkage was confidently excluded and for the remaining family, the number of affected individuals was insufficient to allow an unabiguous result. Conclusion: In these families PSP is not caused by a mutation in the FBN-1 gene. We are testing other candidate genes.