Proteins C and S are vitamin K-dependent proteins with an essential anticoagulant 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 /β°-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.

In this study 21 adults with severe form of sickle cell disease (SCD; sickle cell anaemia, n = 15; Hb S/β°-thal, n = 6) were treated with hydroxyurea (HU) to assess the effectiveness of the drug in managing SCD. The individual dose was selected for each patient. The dose selection was based on the HU clearance study. Thereafter, the patients received daily doses of 15-20 mg/kg body weight. An evaluation data form was filled out at the monthly visit. The severity index (SI) of the disease was determined and haematological parameters including red cell indices, platelet counts, reticulocyte counts, irreversibly sickled cells, red cell deformability, Hb F, Hb F cells, total and direct bilirubin levels were measured prior to treatment, at follow-up intervals during treatment and after cessation of treatment. The trial period lasted 3 months. Statistically significant improvement was observed in the clinical presentation, haematological and biochemical parameters. Hb F level and F cells showed a significant increase in most patients, but to a variable degree. A major resultant effect was an increase in mean cell volume. Our experience shows that HU can be used for the treatment of severe forms of SCD with no major side effects, provided that the doses are monitored and that laboratory investigations are regularly undertaken.