Case Report on Monoclonal Immunoglobulin Deposition Disease (MIDD): A Rare but Not Forgotten Diagnosis

Aim: To report a rare case of biopsy-proven Monoclonal Immunoglobulin Deposition Disease (MIDD) in Malaysia and emphasize the importance of early diagnosis and multidisciplinary management in resource-limited settings.Case Presentation: A 75-year-old Chinese woman with longstanding diabetes and hypertension was referred for progressive renal impairment, marked proteinuria, and elevated serum creatinine. Case ReportInitial workup, including autoimmune and malignancy screening, was unremarkable.Serum free light chain assay revealed markedly elevated kappa and lambda levels.A first renal biopsy was inconclusive, showing only features of diabetic nephropathy.However, due to clinical suspicion, a repeat biopsy with electron microscopy was performed, which revealed linear kappa light chain deposition and characteristic "powdery" electron-dense deposits in the glomerular and tubular basement membranes, consistent with MIDD.The patient was started on a bortezomib-based chemotherapy regimen (Bortezomib, Thalidomide, Dexamethasone) but remained dialysisdependent.Discussion: MIDD is a rare manifestation of Monoclonal Gammopathy of Renal Significance (MGRS) that often mimics diabetic or hypertensive nephropathy, leading to delayed diagnosis.Definitive diagnosis requires immunofluorescence and electron microscopy, which may not be readily available in all settings.Early identification and clone-directed therapy are crucial for halting progression.Conclusion: This case highlights the diagnostic complexity and aggressive nature of MIDD.A high index of suspicion and access to specialized diagnostics are essential.Early, multidisciplinary intervention remains key to improving outcomes, though renal recovery may be limited in advanced disease.