Primary antiphospholipid syndrome in monozygotic twins.

Monozygotic twins, 27 years old, with primary anti-phospholipid syndrome have been described. The first of the twins had obstetric morbidities (one miscarriage at 12 weeks and premature birth of a growth-restricted fetus at 27 weeks secondary to pre-eclampsia) and the second had venous thrombosis. Lupus anticoagulant was present in both and anti-cardiolipin antibodies were present in high titres when re-tested at appropriate intervals. Development of clinical features of APS in monozygotic twins points to an underlying genetic basis in the pathogenesis of anti-phospholipid syndrome.