[Venous branch occlusion due to APC resistance]

Resistance against the anticoagulatory effect of activated protein C (APC) is the most common genetic risk factor for venous thromboembolism. In the industrialized nations, the prevalence is 4-7% of heterozygous symptom carriers and 0.04% individuals with homozygous defect. The hereditary form is conditioned by a single-point mutation in factor V gene, whose molecular characterization became available in 1994. The fact that so far there are no reports about this specific disease in the German literature signifies a lack in the diagnosis of thromboembolic diseases.

For this reason, the disease process of a 43-year-old female patient is reported. The woman came to this hospital for the first time in 1989 presenting a retinal branch vein occlusion. Her history revealed that she had taken hormonal contraceptives. The etiology of the thromboembolism remained unknown. The patient returned in 1997 because of recurrent retinal bleedings. The laboratory data indicated activation of coagulation (APC ratio 1.4). The following molecular characterization confirmed the mutation G 1691 A in factor V gene and the presence of thrombophilia. The ensuing examination of her family for thrombophilia identified one asymptomatic defect carrier among the patient's three children. Alternative methods of contraception were recommended to that daughter to prevent a even higher thrombotic risk and life-threatening complications.

APC resistance seems to be a cause of retinal venous thrombosis in patients younger than 50 years. In patients in whom a familial thrombosis is suspected, the molecular genetic test for factor V Leiden should be obtained. There are no simple methods for the classification of the risks. The etiology of vascular diseases often remains unknown. Therefore it is important in special cases with typical history to keep in mind the APC resistance. Specialized anticoagulative therapy and familial prophylaxis depend on teamwork between ophthalmologists and hemostasiologists. This is decivise for the prevention of blindness.