Membranous nephropathy (MN) concurrent chronic inflammatory demyelinating polyneuropathy (CIDP) in a Bangladeshi male

Introduction: Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disorder of the peripheral nervous system, while membranous nephropathy (MN) is a glomerular disease that may develop from exogenous risks or autoimmune conditions. Their coexistence is extremely rare and poorly understood. Case Report: We report a 55-year-old male from Bangladesh presenting with progressive symmetrical muscle weakness and both motor and sensory impairment in all four limbs. Nerve conduction studies demonstrated features consistent with inflammatory demyelinating polyneuropathy, and cerebrospinal fluid analysis revealed albuminocytological dissociation. The patient also developed nephrotic-range proteinuria; renal biopsy confirmed the diagnosis of membranous nephropathy. He was treated with pulse methylprednisolone and intravenous cyclophosphamide, resulting in improvement in both muscle strength and proteinuria, though sensory deficits persisted. Conclusion: This rare case of concurrent CIDP and MN suggests a shared autoimmune mechanism involving nerves and kidneys. Early recognition and treatment are essential to prevent irreversible neurological and renal damage, especially in resource-limited settings.