Free protein S deficiency in a family with venous thrombosis

[Protein S and ischemic brain disease]

Ischemic brain disease (IBD) represents clinical entity participating with almost 80% in all vascular brain diseases. Ethiopatogenesis and pathophysiology of the ischemic brain disease are apparently most complex in human medicine. In addition to the significant progression in understanding of ethiopatogenesis and pathophysiology of the ischemic brain disease, we are currently aware of the fact that in one third of these patients the source--the disorder or the disease of crucial importance for this sequence of events in the opposing direction cannot be diagnosed with certainty. This case report presents a 32-year-old patient with the verified ischemic lesion of brain parenchyma, in whom the lowered concentrations of protein S were registered by comprehensive clinical and biochemical examinations. The lower concentrations of protein S are a significant co-factor of anticoagulant system, in the absence of other significant diseases, disorders or abnormalities which could ethiopatogenetically be significant for IBD.

Lack of sequence variations in the C4b-BP beta-chain in patients with type III protein S deficiency bearing the Ser 460 to Pro mutation: description of two new intragenic isomorphisms in the C4b-BP beta-chain gene (C4BPB)

Type III protein S (PS) deficiency, characterized by low levels of free PS and normal total PS levels, is often associated with the Ser 460 to Pro substitution. However, some patients bearing this mutation have normal PS levels, suggesting that another gene defect may account for this phenotype. We postulated that this defect was located in the C4b-BP beta-chain gene (C4BPB) and searched for a mutation in the coding regions of this gene in 35 propositi with type III PS deficiency and bearing the Ser 460 to Pro mutation. No mutations explaining the phenotype of type III PS deficiency were identified. We did, however, find two frequent nucleotide changes, one being located in the donor splice site of intron d and the second in the codon corresponding to Asn 137. We used these two polymorphisms to establish C4BPB gene haplotype in five informative type III PS-deficient families and exclude a role of the C4BPB gene in this phenotype of three of them. Finally, increased C4b-BP beta-chain levels were not responsible for the phenotype of type III PS deficiency as the C4BPB haplotype did not correlate with C4b-BP beta-chain levels.

Activated protein C resistance: from phenotype to genotype and clinical practice

The anticoagulant protein C system is an important regulator of the blood coagulation process. Its targets are the procoagulant cofactors factor Va and factor VIIIa, which are cleaved and inactivated by activated protein C, protein S and intact factor V working as cofactors. Genetic defects of protein C or protein S were, together with antithrombin III deficiency, the previously established major causes of familial venous thromboembolism. However, these abnormalities are found in less than 5-10% of patients with thrombosis. Inherited resistance to activated protein C was recently identified as a major risk factor for venous thromboembolism. The activated protein C-resistance phenotype is found in 20-60% of the patients with venous thrombosis, depending on selection criteria and on the prevalence of activated protein C-resistance in the population. The frequency of activated protein C-resistance is 2-10% in the normal populations studied so far. In more than 90% of cases, the molecular background for the activated protein C-resistance is a single point mutation in the factor V gene, which predicts substitution of an arginine at position 506 by a glutamine. Mutated factor V is activated by thrombin or factor Xa in the normal way, but impaired inactivation of mutated factor Va by activated protein C results in a life-long hypercoagulability. Owing to the high prevalence of activated protein C-resistance in the population, it occasionally occurs in patients with deficiency of protein S, protein C or antithrombin III. Individuals with combined defects suffer more severely from thrombosis, and often at a younger age, than those with single defects, suggesting thrombophilia to be a multigenetic disease.