Carrier detection by microsatellite haplotyping in 10 properdin type 1-deficient families.

Properdin deficiency carrier identification is relevant, because properdin-deficient persons have an increased risk of contracting meningococcal disease. Vaccination against meningococcal disease at a young age may provide protection. Accurate detection of this deficiency is needed. Microsatellite haplotyping with the PFCI and PFC2 markers closely linked to the properdin gene locus at Xp11.3-Xp11.23 may offer an easy and accurate identification of carriers of the properdin deficiency gene. The chance to study 91 relatives belonging to 10 families with complete (type 1) properdin deficiency offered a unique opportunity to assess whether properdin type 1 deficiency is associated with a distinct microsatellite haplotype. Haplotyping with the closely linked PFC1 and 2 markers yielded five different haplotypes, which did not support the concept of a founder effect. Among the 28 women carriers, two had normal properdin levels and in five the PFC1,2 polymorphism was not informative owing to homozygosity. Extending the microsatellite haplotyping with three additional markers (DXS1126, DXS426 and DXS7) yielded informative haplotypes in all meioses. We concluded that microsatellite haplo-typing using five markers in close proximity to the properdin gene locus is an accurate method of detecting carriers of the properdin deficiency gene and of properdin-deficient persons within a family at a young age.