Anti-phospholipid and anti-mitochondrial type M5 antibodies in systemic lupus erythematosus.

Fifty-one sera from patients with systemic lupus erythematosus (SLE) were studied in order to evaluate the prevalence of anticardiolipin (ACA) and anti-mitochondrial antibodies (AMA) type M5, and also to explore their relationship with the main serological and clinical features of the disease. A group of 25 (49.0%) patients was found to be ACA positive (IgG or IgG and IgM); in this group we found a significantly higher prevalence of false positive VDRL (p less than 0.01), lupus-like anticoagulant (p less than 0.05), and AMA type M5 (p less than 0.01), but not of anti-ds or ss-DNA antibodies. Three sera positive for ACA, AMA-M5 and anti ss-DNA were absorbed with cardiolipin liposomes. Anti-DNA and AMA-M5 showed only a minimal decrease. Central nervous system involvement and especially seizure syndrome was demonstrated with a higher prevalence in ACA-positive groups (p less than 0.05). Despite the results of absorption experiments, the close relationship between AMA-M5 and ACA, false positive VDRL or lupus-like anticoagulant (LLAC) might justify a speculation on the antiphospholipid nature of this antimitochondrial activity.