Utility of renal biopsy in differentiating idiopathic multicentric Castleman disease from IgG4-related disease.

Idiopathic multicentric Castleman disease (iMCD) is a subtype of human herpesvirus type 8 (HHV-8)-related Castleman disease that causes multi-organ damage, including kidney damage due to polyclonal lymphoproliferation and interleukin (IL)-6-induced cytokine storm. However, its renal pathological findings are unclear. We report the case of a woman in her 80 s who was diagnosed with iMCD based on renal pathological findings. Five years ago, hypergammaglobulinemia was detected, and her renal function declined. Renal biopsy revealed plasma cells infiltrating the stroma. Immunostaining revealed numerous IgG4-positive plasma cells. The serum IgG4 level was high, and she was initially diagnosed with IgG4-related disease (IgG4-RD) and treated with steroids. However, the therapeutic effect was poor. On re-examination, computed tomography revealed lymphadenopathy around the aorta and spleen. Renal histopathology showed numerous IL-6-positive plasma cells. Anemia and C-reactive protein (CRP) positivity persisted despite steroid administration. HHV-8 was negative, and polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes syndrome was not suspected. Thus, iMCD was diagnosed. Based on previous reports, there is no significant difference in IgG4 levels between iMCD and IgG4-RD, and IgG4-positive plasma cell infiltrates were observed in iMCD-affected organs. Therefore, it may be difficult to distinguish iMCD from IgG4-RD. In this case, high-serum IL-6 and CRP were observed, which are usually not seen in IgG4-RD but are common findings in iMCD, leading to the diagnosis. Patients with deep lymphadenopathy may be diagnosed with iMCD based on renal pathological findings. Renal biopsy is recommended for patients with suspected iMCD and decreased renal function.

Detection of Autosomal Dominant Polycystic Kidney Disease by Medical Checkup at an Early Stage.

INTRODUCTION: Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited renal disease. Although abdominal echography during medical checkup may be effective for the early detection of ADPKD, there are no reports of the early detection of ADPKD during medical checkup. We investigated whether there was a difference in renal function and total kidney volume (TKV) at the time of diagnosis due to differences in diagnostic triggers for ADPKD. METHODS: A total of 34 patients diagnosed with ADPKD between January 1, 2010, and December 31, 2020, at the Department of Nephrology, Shimane University Hospital, were included. The triggers for diagnosis of the renal cyst(s) were usually unintentional findings. These included findings observed upon routine medical checkups, computed tomography, or abdominal echography during examination for other diseases (incidental detection group) and cases referred to our department for renal dysfunction (renal dysfunction group), and "other" group. We compared the renal dysfunction group and the incidental detection group. RESULTS: The estimated glomerular filtration rate (eGFR) at diagnosis was significantly higher in the incidental detection group. The TKV was significantly lower in the incidental detection group than in the other group. The number of patients with eGFR > 45 mL/min/1.73 m2, for which tolvaptan was safe and effective, was significantly higher in the incidental detection group than in the renal dysfunction group. CONCLUSION: Our study shows that medical checkup enables early detection of ADPKD. This is important because ADPKD may have serious complications. The present study did not examine the age at which abdominal echography screening for the early detection of ADPKD was more useful or cost-effective; thus, further research is needed to ascertain this.