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–β2 -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.