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A 43-year-old male experienced renal infarction (RI) following left upper lobectomy for lung cancer. The patient complained of acute-onset severe left flank pain on the 14th postoperative day. A contrast-enhanced computed tomography (CT) of the abdomen revealed RI by a large wedge-shaped defect in the left kidney. A chest CT scan located the thrombus in the stump (a blind-ended vessel) of the left superior pulmonary vein. Therefore, thromboembolic RI caused by pulmonary vein thrombosis was suspected. Anticoagulation therapy was initiated with heparin and warfarin to treat RI and to prevent further embolic episodes. Two months later, pulmonary vein thrombosis had resolved without the appearance of additional peripheral infarction. This case emphasizes the need to consider thrombus in the stump of the pulmonary vein as a cause of RI.

Coexistence of anti-glomerular basement membrane (anti-GBM) disease with anti-neutrophil cytoplasmic antibody (ANCA) is occasionally reported and termed "double positive" disease. Interestingly, the majority of "double positive" ANCA is myeloperoxidase (MPO)-ANCA, and some of the MPO-ANCA-positive cases reveal intrarenal arteritis indicating an ANCA-associated renal lesion. In contrast, proteinase 3 (PR3)-ANCA-positive "double positive" disease had rarely been reported, and as far as we know, none of the cases showed intrarenal arteritis. Herein, we report a case of PR3-ANCA-positive "double positive" anti-GBM disease presenting with pulmonary-renal syndrome and hemolytic uremic syndrome. The kidney biopsy showed crescentic glomerulonephritis, intrarenal arteritis, and thrombotic microangiopathy. This case newly describes PR3-ANCA-associated intrarenal arteritis in "double positive" anti-GBM disease.

Background Immunoglobulin heavy-and-light-chain amyloidosis (AHL amyloidosis) is a newly established disease entity where both the immunoglobulin heavy-chain and light-chain compose amyloid fibrils. The immunoglobulins responsible for the amyloid fibrils are generally identified by immunostaining and/or laser microdissection-liquid chromatography-tandem mass spectrometry (LMD-LC-MS/MS). However, both techniques do not biochemically differentiate immunoglobulins that formed amyloid fibrils from non-responsible immunoglobulins. Case presentation We herein report a case of 67-year-old female patient with renal amyloidosis due to lymphoplasmacytic lymphoma secreting monoclonal immunoglobulin M (IgM)-kappa. Renal immunostaining monotypically positive for IgM-kappa and LMD-LC-MS/MS identification of mu heavy-chain and kappa light-chain were consistent with the diagnosis of AHL amyloidosis. In order to confirm that both the immunoglobulin heavy-chain and light-chain were forming amyloid fibrils, we performed LC-MS/MS of renal amyloid fibrils isolated by the traditional amyloid purification method. The additional LC-MS/MS identified kappa light-chain only without any heavy-chain component. These results were suggestive that amyloid fibrils were composed by kappa light-chain only and that the mu heavy-chain identified by immunostaining and LMD-LC-MS/MS was derived from the non-specific co-deposition of monoclonal IgM-kappa. Conclusion The case was AL amyloidosis with non-amyloid forming monoclonal immunoglobulin deposition. While immunostaining and LMD-LC-MS/MS are irreplaceable techniques to classify amyloidosis, confident exclusion of the present condition should be required to diagnose AHL amyloidosis.