[Immune-mediated necrotizing myopathy: clinical and histopathological correlation]

Immune-mediated necrotizing myopathy (IMNM) is a variant of inflammatory myopathies, characterized by muscle fiber necrosis and regeneration with minimal inflammatory infiltration, associated with a potentially severe clinical course and difficult management. We report the case of a 64-year-old woman with a history of type 2 diabetes mellitus who presented with progressive proximal weakness, dysphagia, and prostration of one month's duration. She developed severe muscle involvement requiring subsequent mechanical ventilation. Initial studies showed markedly elevated creatine phosphokinase (CPK) levels (>10 000 U/L), and muscle biopsy revealed fiber necrosis and regeneration with scant inflammatory infiltrate, consistent with IMNM. Intensive treatment with methylprednisolone pulses and intravenous immunoglobulin was initiated, followed by the addition of methotrexate, azathioprine, and rituximab. Under this combined regimen, the patient showed a favourable evolution with progressive decline of CPK, functional recovery of muscle strength, and improvement of dysphagia, being discharged in ambulatory conditions with minimal assistance. An interdisciplinary approach and early implementation of intensive immunosuppression are essential to reverse unfavourable progression and optimize the functional prognosis of these patients.