Multicentric Castleman’s disease (MCD) is a benign lymphoproliferative disorder with heterogenous clinical symptoms, and involves systemic organs in addition to lymph nodes. Herein, we present the case of a 55-year-old man with MCD characterized by an extensive infiltration of IgG4+ plasma cells in the kidneys. The patient presented to our hospital with a high fever and diarrhea. On admission, laboratory analysis revealed anemia, renal dysfunction (eGFR 30 mL/min/1.73 m²), polyclonal gammopathy (IgG 7130 mg/dL), elevated serum IgG4 level (2130 mg/dL), and increased C-reactive protein (8.0 mg/dL). An enlargement of lymph nodes in the axillary, mediastinal, para-aortic, and inguinal regions was observed on abdominal computed tomography. Axillary lymph node biopsy revealed interfollicular expansion due to dense plasma cell infiltration. Renal biopsy demonstrated significant plasma cell infiltration into the tubulointerstitium. Immunohistochemical analysis showed a 40% IgG4-positive/IgG-positive plasma cell ratio, meeting the diagnostic criteria for an IgG4-related disease. Amyloid A deposition was observed along vessel walls, and immunofluorescence analysis indicated granular positivity of IgG and C3 along the glomerular capillary wall. Elevated levels of interleukin-6 (21 pg/mL) and vascular endothelial growth factor (VEGF; 1210 pg/mL) were noted. Based on these findings, and the histological finding of the lymph node biopsy, idiopathic MCD was diagnosed. Corticosteroid monotherapy was only partially effective. Subsequently, tocilizumab administration was initiated, leading to sustained remission, even after discontinuation of prednisolone. Due to the diverse responses to steroid therapy and the varying prognoses observed in MCD and IgG4-related disease, it is essential to carefully diagnose MCD by thoroughly assessing the organ distribution of the disease, its response to steroid therapy, and any additional pathological findings.

TAFRO (Thrombocytopenia, Anasarca, Fever and/or elevated C-reactive protein, Renal dysfunction or Reticulin fibrosis, and Organomegaly) syndrome is a unique systemic inflammatory disease, which has recently been proposed from Japan. We report a case showing TAFRO symptoms, the patient’s condition of which allowed histopathological examinations of several biopsy tissues including the kidney. A 37-year-old man was admitted to our hospital for evaluation of fever of unknown origin, pleural effusion and ascites, renal dysfunction, and lymphadenopathy. Serum IL-6 and VEGF were elevated. Histopathologic findings of the lymph node resembled those of mixed type Castleman disease. The bone marrow biopsy specimen revealed normocellular marrow with a mildly increased number of megakaryocytes, but without obvious fibrosis. The renal biopsy material showed glomerular microangiopathy with double contour of the capillary loops and mesangiolysis. In immunohistochemistry, VEGF was retained in podocytes, whereas IL-6 expression was not limited to the specific sites. Glomerular microangiopathy is regarded as a crucial change in TAFRO syndrome, which should be studied further with regard to VEGF and IL-6.

Background and Clinical Significance: Although dietary supplements have often been deemed safe, some have been linked to drug-induced nephropathy due to their diverse ingredients. The aim of this report is to enhance clinical awareness of a novel and emerging cause of Fanconi syndrome due to red yeast rice supplements and to contribute new histopathological and clinical data. Case Presentation: We report two cases of renal dysfunction and Fanconi syndrome associated with the use of red yeast rice supplements. Both patients presented with renal impairment accompanied by elevated markers of tubular injury, hypouricemia, hypokalemia, and glucosuria, consistent with Fanconi syndrome. Following the discontinuation of the red yeast rice supplement and initiation of steroid therapy, Fanconi syndrome resolved, however, moderate renal dysfunction persisted. Urinary NGAL levels improved after treatment in both cases. KIM-1 normalized in one case but remained elevated in the other. Uromodulin recovery was complete in one case and partial in the other. Renal biopsy revealed mild tubulointerstitial nephritis, with notable shedding of proximal tubular epithelial cells. Immunohistochemical analysis demonstrated reduced expression of URAT-1, Na-K ATPase, and Na-Pi IIa in some tubules. Conclusions: These findings suggest that renal injury induced by red yeast rice supplements is mediated by direct proximal tubular necrosis caused by a harmful substance in the supplement, resulting in persistence of tubular dysfunction.