Analysis of MPO-ANCA subtypes in a patient with propylthiouracil-induced vasculitis with multiple complications

We report a 16 year-old girl with propylthiouracil (PTU)-induced antineutrophil cytoplasmic antibody (ANCA)-positive glomerulonephritis combined with Henoch-Schönlein purpura nephritis (HSPN) and antiphospholipid syndrome (APS).

The patient had Graves' disease and had been treated with PTU for about 6 years. She complained of arthralgia, epigastralgia, purpura of the lower extremities, anemia, and abnormal urinalysis. Lupus anticoagulant was positive. Additionally, a high level of anti-myeloperoxidase (MPO) antibodies (IgG) and a low level of coagulation factor XIII were recognized. She had several complications including lung bleeding, lacuna infarctions of the right frontal and parietal brain lobes, and deep vein thrombosis of the left lower extremity. We studied tissue histology and carried out MPO-ANCA subtype analysis by immunofluorescence and flow cytometry and MPO-ANCA epitope analysis.

Histologically, purpura showed leukocytoclastic vasculitis with perivascular depositions of IgA and complement C3. Renal biopsy showed necrotizing glomerulonephritis with crescents and mesangial IgA deposits. Notably, IgG, IgM, and IgA ANCA were detected in the patient's serum by flow cytometry and immunofluorescence. We diagnosed an overlap syndrome of ANCA-positive vasculitis, HSPN, and APS. A change in the reactivity of MPO-ANCA from recognition of only the Hg epitope in the C-terminal region to recognition of multiple MPO epitopes was accompanied by a remission of symptoms.

This report may provide a very rare description of an overlap syndrome of PTU-induced ANCA vasculitis, HSPN, and APS in which not only IgG ANCA but also IgA and IgM ANCA were found. Epitope analysis may be a useful marker for disease-monitoring of PTU-induced ANCA-positive vasculitis. This case may provide insight into the pathological mechanism underlying each of these diseases.