RESUMO
Five unrelated families with Puerto Rican ancestry were identified as having at least one member with bleeding due to a prothrombin deficiency. Genetic prothrombin deficiencies are extremely rare, but at the University of Puerto Rico Hemophilia Center, prothrombin deficiency is the third most common congenital coagulation factor deficiency. Because Puerto Rico is relatively isolated, there was a reasonable expectation of a founder effect. Prothrombin genes from probands and their parents were directly sequenced from PCR amplified exons using forward and reverse primers. Four novel prothrombin mutations were identified. The first, a G-->A substitution at DNA position 10150 predicting an Arg457-->Gln (R457Q) replacement, is common to all five families. In two of the families, the proband children are homozygous for R457Q. In the other three families, the probands are compound heterozygotes for R457Q and one of the other three mutations, which include another point mutation (gamma16Q), a deletion and a splice junction mutation. The two point mutations have been designated Puerto Rico I and Puerto Rico II. The crystal structure of alpha-thrombin predicts that the R457Q mutation removes a salt bridge that links the A- and B-chains of thrombin. The primary effect of this defect appears to be destabilization of the circulating prothrombin, creating a moderate hypoprothrombinemia. However, prothrombin antigen/activity ratios indicate a dysprothrombinemia as well, most likely due to the inability of R457Q prothrombin to activate fully to thrombin.
Assuntos
Hipoprotrombinemias/genética , Mutação de Sentido Incorreto , Adolescente , Adulto , Análise Mutacional de DNA , Saúde da Família , Feminino , Heterozigoto , Homozigoto , Humanos , Masculino , Mutação Puntual , Polimorfismo de Nucleotídeo Único , Conformação Proteica , Protrombina/química , Protrombina/genética , Porto RicoRESUMO
Skin necrosis and priapism are unusual complications of warfarin therapy. We report a teenager with warfarin-associated skin necrosis and priapism who was subsequently found to be a compound heterozygote for protein C deficiency and a heterozygote for the factor V Leiden mutation.
Assuntos
Anticoagulantes/efeitos adversos , Toxidermias/etiologia , Priapismo/induzido quimicamente , Varfarina/efeitos adversos , Adolescente , Toxidermias/complicações , Toxidermias/patologia , Fator V/genética , Humanos , Masculino , Necrose , Priapismo/complicações , Deficiência de Proteína C/complicações , Trombofilia/genéticaRESUMO
OBJECTIVE: The objective of this study was to determine the cause of purpura fulminans, disseminated intravascular coagulation, or thrombosis in seven children with varicella. All children were found to have a lupus anticoagulant and acquired protein S deficiency. Thrombosis in five children was associated with presumed or documented infection with streptococcus. STUDY DESIGN: Coagulation tests included determinations of the activated partial thromboplastin time, the prothrombin time, the dilute Russell viper venom time, the prothrombin F 1 + 2 fragment, the C4b-binding protein (C4b), total and free protein S antigen, and clotting activities of factors II, V, VII, and X and of protein C and protein S. Autoantibodies to phospholipids, cardiolipin, and protein S were determined in enzyme-linked immunosorbent assays. RESULTS: All children had a lupus anticoagulant and acquired protein S deficiency. Thrombosis in five children was associated with presumed or documented infection with streptococcus. All children transiently expressed free protein S deficiency, elevated levels of IgG, IgM, or both binding to protein S, the lupus anticoagulant, and increased concentration of the F 1+2 fragment. Four children also had antiphospholipid or anticardiolipin antibodies. In one child a purified IgG fraction cross-reacted with both protein S and a specific varicella antigen. CONCLUSIONS: A subset of children with varicella infection, some of whom are coinfected with streptococcus, are prone to development of a lupus anticoagulant and an autoantibody to protein S, which results in acquired free protein S deficiency. Such children are at risk of having life-threatening thrombotic events.