Fatal Case of Crystalglobulin-Induced Nephropathy with Cardiac Nonamyloid Immunoglobulin Deposition Disease

Introduction: Crystalglobulin-induced nephropathy (CIN) is a rare renal disorder associated with multiple myeloma(MM). Crystal-induced organ damage occurs in various organs, and the diagnosis is based on the presence of crystals in the affected tissues. In the context of cardiac deposition of monoclonal immunoglobulin, AL amyloidosis and monoclonal immunoglobulin deposition disease (MIDD) can be differentiated. When amyloidosis is excluded and light and/or heavy chain immunostaining is positive, the cardiac variant of MIDD, cardiac non-amyloid immunoglobulin deposition disease (CIDD), is diagnosed. There has never been a report of CIN combined with CIDD. Here, we report a case of severe acute kidney injury with gradually reduced cardiac function diagnosed as CIN combined with CIDD. Case Description: A 55-year-old Asian woman presented with leg edema two weeks after COVID-19 infection. She exhibited renal dysfunction with Cr of 1.89 mg/dL, urinary protein 3+, and urinary occult blood 2+, and presented to our hospital. At the time of admission, her Cr was 2.4 mg/dL, IgG-λ M-protein was positive, and cryoglobulin was negative. Despite the initiation of hemodialysis due to anuria shortly after admission, her condition progressively deteriorated. Renal biopsy revealed a MPGN-like pattern of injury with proteinaceous thrombi in the glomeruli, arterioles, and interlobular arteries. Immunofluorescence staining was positive for IgG1 and λ light chains, consistent with monoclonal proteinaceous thrombi. Electron microscopy showed crystal-like structures in the glomeruli and arteries. Myocardial biopsy revealed λ light chain deposition, confirmed by immunoelectron microscopy. Bone marrow biopsy showed 10% plasma cells. The patient was treated with dexamethasone, daratumumab, and bortezomib as for MM. However, her renal function didn't recover. With a gradual decline in cardiac function, lactic acidosis and hypotension persisted, and she passed away. Discussion: Both CIN and CIDD are rare diseases associated with monoclonal protein. CIN might involve the cardiac system as infarction. However, in this case, the same monoclonal protein affected the kidneys as crystals but directly damaged cardiomyocytes as intact light chains. Evaluation of each affected organ might benefit the patient for accurate diagnosis and appropriate treatment.