Successful 6-year follow-up of treatment for IgA nephropathy complicated by IgA-λ monoclonal gammopathy with multi-system damage: a case report.

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerular disease in China and a major contributor to the need for renal transplantation. IgAN is characterized by the mesangial deposition of IgA-dominant or IgA-specific immune complexes, accompanied by complement components, and is recognized as a polyclonal autoimmune disorder largely restricted to the kidneys. But approximately 9.2% of patients with IgAN demonstrate evidence of monoclonal IgA deposition, making IgAN with monoclonal IgA deposition and related nephropathies clinically challenging conditions. Our report describes a rare case of IgAN complicated by IgA-λ monoclonal gammopathy of rheumatologic significance(MGRhS). Although the renal pathology in the patient did not suggest monoclonal gammopathy of renal significance (MGRS), the patient showed a poor initial response to corticosteroid, immunosuppressive therapy, and rituximab, followed by progressive clinical deterioration with multi-system damage, including persistent fever, normocytic anemia, recurrent hemoptysis, and sensorimotor peripheral neuropathy. Clone-directed treatment targeting the underlying plasma cell disorder led to marked clinical improvement. The patient subsequently underwent kidney transplantation with favorable outcomes after three years. Over a three-year follow-up period after transplantation, graft function remained stable and no evidence of disease recurrence was detected. In conclusion, when renal pathology in IgAN does not fulfill diagnostic criteria for MGRS, careful evaluation for IgA monoclonal gammopathy is warranted. It may represent MGRhS associated with multisystem involvement. Complete elimination of the monoclonal protein before transplantation is critical for achieving sustained allograft survival.