Acute kidney injury secondary to crystalline cryoglobulinemic glomerulonephritis type I: a case report and literature review.

BACKGROUND: Type I cryoglobulinemia consists of a single monoclonal immunoglobulin and can induce small-vessel vasculitis with renal involvement. Cryoglobulinemic glomerulonephritis is a rare manifestation, pathologically characterized by membranoproliferative glomerulonephritis (MPGN). In this report, we present a case of type I cryoglobulinemic renal injury characterized by crystalline cryoglobulinemic glomerulonephritis type I. Our objective is to provide a detailed insight into the presentation, underlying diseases, diagnosis, treatment, and outcomes of crystalline cryoglobulinemic glomerulonephritis type I.Case presentation: A 38-year-old man presented with acute kidney injury (AKI) without any other systemic symptoms. A kidney biopsy confirmed the presence of abundant pseudothrombi within the glomerular capillary lumens, with no significant proliferative lesions observed. Immunofluorescence microscopy (IF) demonstrated strong, diffuse, homogeneous staining for IgG1 and Lambda light chain. Electron microscopy revealed a microtubular substructure characteristic of nephropathy. Following the initial course of rituximab, plasma exchange (PE), and methylprednisolone, the treatment yielded successful results. However, renal dysfunction recurred 18 months later, prompting a second renal biopsy, which exhibited findings similar to the first. Additionally, bone marrow biopsy identified an aberrant monotypic plasma cell clone. Subsequently, daratumumab therapy was initiated, leading to a recovery in kidney function. CONCLUSION: In nephropathies associated with crystalline cryoglobulinemic glomerulonephritis type I, renal and bone marrow biopsies play a crucial role in establishing the diagnosis and determining the optimal therapeutic approach. It is essential to consider primary diseases prior to selecting the initial management strategy.