A Case of Familial Antithrombin III Deficiency in an English Family

In this case a mother and three of her four sons living in southern England are affected. The mother’s At III level measured as progressive At III (chromogenic substrate) was 51% heparin cofactor 61% and by immunological assay 53%. Three sons have At III levels of 48%, 55%. and 56%, (progressive), 43%, 54% and 51% (heparin eofarctor), and 53%, 57% and 51% (immunological) respectively. By a clotting assay the sons were found to have values of 60%, 56% and 63% Crossover immmunoelectrophoresis against At III antisera in the presence of heparin (Sas et al, 1975) showed no difference from normal, distinguishing this form of deficiency from Antithrombin Budapest. A sister of the mother and four other members of the family had normal At III levels. All members of the family had normal levels of α1 antitrypsin and α-2 macroglobulin as measured by the radial immunodiffusion technique. Clinically all the At III deficient sons have had recurrent DVT and have grade IV post phlebitic legs. One son has also had in addition, an inferior vena cava thrombosis (at age of 8 years) and mesenteric thrombosis (at age of 30 years). The development of a thrombosis at age 8 may illustrate that symptoms of At III deficiency may not be confined only 8 adulthood. Affected members of the family are at present: on a regimen of self administered low-dose subcutaneous heparin.