Clinical Characteristics and Renal Outcomes in Patients with IgM Nephropathy: A Retrospective Single-Center Study

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Background: Defining immunoglobulin M (IgM) nephropathy as a discrete clinical disorder remains controversial, with limited documentation in Saudi Arabian patients. Aim: This study analyzes the clinical and pathological features, as well as the prognosis, of IgM nephropathy in the Saudi population. Methods: This study is conducted as a retrospective descriptive study at the nephrology unit of King Saud University Medical City in Riyadh. The study included individuals with biopsy-proven IgM nephropathy from 2016 to 2024. Stringent diagnostic criteria were employed, focusing on immunofluorescence positivity (IgM 1+ to 3+). Clinical data were collected from a kidney biopsy registry from the pathology department at King Saud University, and renal pathology was evaluated by a single expert renal pathologist for various features, including mesangial cell proliferation and glomerulosclerosis. Results: We analyzed a total of 15 patients with IgM nephropathy (n = 15), with a median age at diagnosis of 4 years (IQR: 2-8) and a male predominance (80%). Patients were categorized into early childhood onset (<4 years, 46.7%) and late childhood onset (≥4 years, 53.3%). Common manifestations included nephrotic syndrome (93.3%) and generalized body swelling (66.7%), with lower limb edema reported in all patients (100%). Nephrotic-range proteinuria was present in 93.3%, with preserved renal function (median eGFR: 158 mL/min/1.73m²). Biopsy results for nine patients revealed mesangial proliferation in 66.7%. The overall relapse rate was 93.3%, with early-onset patients exhibiting higher rates of steroid resistance and more frequent relapses. Conclusion: This study enhances the understanding of IgM nephropathy in Saudi Arabia, indicating that early onset may be associated with a more aggressive disease course and higher relapse rates, highlighting the need for early identification of high-risk patients. Additionally, the use of rituximab in refractory cases may present a promising option for further evaluation.

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