Isolated type 5 antimitochondrial autoantibodies are associated with a history of thrombocytopenia and fetal loss.

OBJECTIVE: To report an unusual case of clinical antiphospholipid syndrome seen with recurrent fetal loss, chronic thrombocytopenia, and recurrent idiopathic thrombocytopenic purpura, in which the only laboratory marker was M5-type antimitochondrial autoantibodies (AMA). DESIGN: Case report. SETTING: University general hospital, tertiary level of clinical care. Institutional practice. PATIENT(S): A 65-year-old woman with antiphospholipid syndrome associated with autoimmune polyglandular syndrome of IIIC type. INTERVENTION(S): Clinical history and biochemical and immunologic markers. MAIN OUTCOME MEASURE(S): The presence of M5-type AMA in clinical antiphospholipid syndrome isolated by indirect immunofluorescence. RESULT(S): During the 10-year follow-up, immunologic studies detected a persistent positive M5-type AMA at high titer (1/640), antithyroid antibodies, anti-gastric parietal cells, and anti-intrinsic factor. Antinuclear, anti-DNA, and antiphospholipid (anticardiolipin, anti-beta(2)-glycoprotein I) autoantibody tests were all repeatedly negative. Results of coagulation studies and negative lupus anticoagulant were normal on several occasions. CONCLUSION(S): Our findings suggest the necessity of determining M5-type AMA in the study panel of antiphospholipid syndrome diagnosis, particularly in the absence of other typical autoantibodies.