Renal histological continuum of TAFRO syndrome: A case report and literature review.

TAFRO syndrome is a rare systemic inflammatory disorder that is characterized by thrombocytopenia, anasarca, fever, reticulin fibrosis, and organomegaly. Progressive renal involvement is frequently observed in patients with TAFRO syndrome, and the renal histological findings remain limited. A 52-year-old man with thymoma that was detected by chest computed tomography was admitted to our hospital because of dyspnea and abdominal distension. He had a rapid reappearance of pleural and abdominal effusion following repeated puncture with inflammation and kidney involvement on admission. Renal histology showed glomerular lesions denoting diffuse endocapillary proliferative glomerulonephritis, without any crescentic glomeruli, which was diagnosed as thrombotic microangiopathy (TMA)-like glomerulopathy. Together with histological findings of thymoma and progressively emergent thrombocytopenia, the patient was diagnosed with TAFRO syndrome. Corticosteroid and tocilizumab administration ameliorated the renal insufficiency and his clinical condition relevant to TAFRO syndrome, but there was a rapid concomitant appearance of massive proteinuria. A second renal biopsy revealed membranoproliferative glomerulonephritis (MPGN)-like glomerulopathy with de novo sclerosing and crescentic glomeruli development. Patients with TAFRO syndrome show glomerular lesions that are consistent with TMA- or MPGN-like lesions, but their clinical data are similar between the two glomerulopathies. It remains controversial whether the two are a histopathological continuum or distinct diseases. This case shows that glomerular lesions had TMA-like glomerulopathy in the acute stage of TAFRO syndrome, while the histopathology pattern favors MPGN in the chronic stage, as confirmed by repeated renal biopsies. TAFRO syndrome disease activity may not always correspond to that of glomerulopathy that is associated with TAFRO syndrome.