Genetic and phenotypic analysis of a large (122-member) protein S-deficient kindred provides an explanation for the familial coexistence of type I and type III plasma phenotypes

Research output: Contribution to journalArticle


Protein S deficiency is a known risk factor for thrombosis. The coexistence of phenotypic type I (reduction in total and free antigen) and type III (reduction in free antigen only) protein S deficiencies in 14 of 18 families was recently reported. We investigated the cause of this phenotypic variation in the largest of these families (122 family members, including 44 affected individuals) using both molecular genetic and phenotypic analysis. We have identified a sole causative mutation (Gly295Val) in three family members representative of the variable phenotype. Complete cosegregation of the mutation with reduced free protein S antigen levels was found, regardless of the total antigen level. Analysis of phenotypic data showed high correlations between total protein S antigen and age in both normal and protein S-deficient family members, irrespective of gender. Free protein S antigen levels were not influenced by age, a finding explained by an association between beta-chain containing C4b-binding protein (C4bBP-beta+) antigen levels and age. We propose that the identified Gly295Val mutation causes quantitative, or type I, protein S deficiency, and that as age increases the total protein S antigen level normalizes with respect to the reference plasma pool, giving rise to a type III protein S-deficient phenotype.


External organisations
  • Charing Cross and Westminster Medical School
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Medicinal Chemistry


  • binding protein, complement component C4b, protein S, adolescent, adult, aged, article, child, clinical article, controlled study, female, gene mutation, genotype, human, male, phenotype, priority journal, protein S deficiency
Original languageEnglish
Pages (from-to)4364-4370
Number of pages7
Issue number12
Publication statusPublished - 1997 Jun 15
Publication categoryResearch