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In 30 children with homozygous β-thalassemia the hemostasis screening tests (bleeding time, PT, PTT), platelet count and specific assays of clotting factors were carried out 25 days after their last transfusion. PT, PTT, and bleeding time showed minor variations; considerable thrombocytosis was found in splenectomized patients. Factors IX and XII were decreased in a high proportion of patients, the vitamin K-dependent factors (II, VII, IX, X) were slightly reduced and factors I, V and VIII remained within the normal range in a majority of patients. Hepatic failure resulting in defective protein synthesis does not explain the more marked impairment of factors XI and XII, which might be secondary to activation of the intrinsic coagulation and/or kallikrein systems following intravascular haemolysis and multiple blood transfusions.

This study was carried out on twenty-eight Sardinian subjects undergoing massive intravascular hemolysis after ingestion or inhalation of fava beans. The patients were all deficient in glucose-6-phosphate dehydrogenase but otherwise hematologically normal when investigated after the acute hemolytic episode. Prothrombin time, thrombin time and activated partial thromboplastin time were found to be shortened in the days following the hemolytic crisis. Marked increase of factor VIII (antihemophilic factor) and fibrinogen was also observed, together with a less pronounced rise of factor V. The other clotting factors were within the normal range, and fibrinogen degradation products were not present in serum. The observed rise was found to be generally proportional to the degree of red cell destruction. Progressive normalization of the abnormal parameters followed the recovery from acute hemolysis. These observations are discussed in relation to previous findings and to the occurrence of intravascular coagulation following massive red cell destruction.

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