Biopsy-proven Systemic Lupus Erythematosus and Antineutrophil Cytoplasmic Antibody-associated Vasculitis Overlap Syndrome Developed during Propylthiouracil Therapy: A Case-based Review.

A 31-year-old woman who had been receiving propylthiouracil (PTU) treatment for Graves' disease was referred to our hospital for the evaluation of hematuria and proteinuria. Laboratory tests showed positivity for myeloperoxidase-antineutrophil cytoplasmic antibody (ANCA), proteinase 3-ANCA, and anti-double-stranded DNA antibodies. A kidney biopsy revealed immunocomplex-mediated mesangial proliferative glomerulonephritis, consistent with lupus nephritis (LN) diagnosis. Additionally, tubulitis, peritubular capillaritis without immune complex deposition, and medullary angiitis were observed. We herein describe a case of overlap syndrome of LN and ANCA-associated vasculitis (AAV) that developed during PTU therapy. A detailed histological evaluation, including an examination of the renal medulla, may aid in distinguishing between AAV, LN, and overlap syndromes.