Finding the ideal balance between efficacy and safety of immunosuppression is challenging, particularly in cases of severe TAFRO syndrome. We herein report a 60-year-old man diagnosed with grade 5 TAFRO syndrome mimicking hepatorenal syndrome that was successfully treated by glucocorticoid, tocilizumab, and cyclosporin despite virus infection. Furthermore, by examining 14 peer-reviewed remission cases, we revealed that the recovery periods among inflammation, renal dysfunction, and thrombocytopenia were quite different, with recovery from thrombocytopenia notably slow. All patients requiring dialysis were successfully withdrawn from dialysis, and the reversibility from kidney injury was good. This clinical information will help clinicians plan treatments and tailor the intensity of immunosuppression.

Background Lately, monoclonal gammopathy of renal significance (MGRS) has been defined as a group of renal disorders that are strongly associated with monoclonal protein, including amyloid immunoglobulin light chain (AL) amyloidosis. Amyloid myopathy is rare (1.5% of all patients with amyloidosis) and the prognosis is poor. Furthermore, only approximately 20% of patients with amyloid myopathy are reported to have renal involvement, indicating a lack of data in the literature. Case presentation Here, we report a rare case of MGRS-related AL amyloidosis complicated by amyloid myopathy that presented with muscle weakness in the upper and lower limbs, neck and fingers, and nephrotic syndrome. Blood, urine, and bone marrow examination revealed monoclonal gammopathy of undetermined significance (MGUS) (Bence Jones protein-lambda). Muscle biopsy of the vastus lateralis muscle demonstrated amyloid proteins in the sarcolemma and in the blood vessel walls on Congo red staining, suggesting amyloid myopathy, and tiny inclusions in fibers on modified Gomori trichrome stain. Although we thought they were reminiscent of nemaline bodies, we could not confirm the nature of this structure. Renal biopsy demonstrated amyloid proteins in the mesangial region, part of the capillary walls, and the blood vessel walls on direct fast scarlet staining. As these amyloid proteins were positive for p-component staining and negative for amyloid A staining, β2-microglobulin, and pre-albumin, and as lambda light chains were positive in the mesangial region, we diagnosed the patient with MGRS-related AL amyloidosis. Although he was treated with melphalan and dexamethasone, his symptoms did not improve. Conclusions AL amyloidosis involving the kidneys and muscles has a poor prognosis, and a delayed diagnosis of amyloid myopathy is common because of its rarity and frequent misdiagnosis, which increases organ function deterioration. Therefore, early detection, therapeutic intervention, and careful follow-up are crucial.

Dialysis patients have an increased risk of coronavirus disease 2019 (COVID-19)-related mortality. Acute heart failure is a frequent, lethal complication of COVID-19, and it is a risk factor for mortality in hemodialysis patients. Therefore, it is crucial to rapidly distinguish heart failure from COVID-19 pneumonia. Here, we report a case of two episodes of acute dyspnea that were induced by COVID-19 in a peritoneal dialysis (PD) patient. The first episode of acute dyspnea was an exacerbation of heart failure caused by COVID-19 when the patient had a volume overload status due to a peritoneal dialysis catheter malfunction. Heart failure induced by a catheter malfunction was due to omental wrapping, and it was treated with ultrafiltration by hemodialysis and mini-laparotomy. The patient's acute dyspnea was immediately resolved. The second episode of acute dyspnea was caused by COVID-19 pneumonia, which occurred 1 week after the first episode. This case suggests the importance of identifying heart failure and beginning adequate treatment, in COVID-19 patients with PD.

Rosai-Dorfman-Destombes disease (RDD) is a non-Langerhans cell histiocytosis characterized by the accumulation of histiocytes inside the lymph nodes or extranodally. The association between RDD and IgG4related disease (IgG4-RD) is discussed. We herein report a case of RDD manifesting as acute tubulointerstitial nephritis mimicking IgG4-RD. The first renal biopsy showed severe tubulointerstitial nephritis with infiltration of S100-positive histiocytes and IgG4-positive plasma cells; storiform fibrosis and obliterative phlebitis were not confirmed. After prednisolone therapy, IgG4-positive cells and S100-positive histiocytes were decreased, but the IgG4/IgG ratio increased despite clinical improvement. These findings indicated extranodal RDD in the kidney presenting as tubulointerstitial nephritis.