Blood proteins C and S in sickle cell disease.

Proteins C and S are vitamin K-dependent proteins with an essential anti-coagulant function. Protein C exists in an inactive form and is activated by a thrombin-thrombomodulin complex. Protein S combines with protein C and forms a stoichiometric complex which regulates coagulation in the presence of calcium. As patients with sickle cell disease (SCD) bear a high risk of developing thrombo-embolic disorders, we studied the coagulation derangement in 100 patients and 40 normal age- and sex-matched controls. The patients were clinically assessed and classified into sickle cell homozygotes (Hb SS), Hb S heterozygotes (Hb AS) and double heterozygotes for Hb S/beta 0-thalassaemia based on haematological parameters, red cell indices, Hb A2 and F levels and genetic studies. The proteins C and S were estimated and related to the type of the gene defect. The results showed significantly reduced levels of proteins C and S in SCD patients with the highest prevalence of deficiency in patients with a severe disease and frequent episodes of crisis. However, no significant differences were encountered in the level of proteins C and S in the same patients during the steady state and during episodes of crisis. It was concluded that the lower protein C and S levels in SCD is either due to decreased production or increased consumption though this reduction does not seem to play a role in producing thrombo-embolic disorders.