Polymyositis secondary to paroxysmal nocturnal hemoglobinuria (PNH): A case report.

Abstract

We present the case of a 35-year-old patient with a previous diagnosis of paroxysmal nocturnal hemoglobinuria (PNH), treated with immunosuppressants and bone marrow stimulation therapy. She was admitted to the institution with severe pancytopenia, extreme fatigue, signs of hemorrhage and desquamative lesions, evolving to septic shock, neurological involvement and progressive proximal muscle weakness. Clinical, imaging and muscle biopsy findings confirmed the diagnosis of polymyositis, a rare entity in patients with PNH. Treatment with prednisone and eculizumab was started, achieving an initial partial improvement. Adequate functional status and no signs of polymyositis were achieved under monoclonal antibody therapy. This case highlights a possible pathophysiological interaction between chronic complement activation in PNH, prolonged immunosuppression and the development of an inflammatory autoimmune disease such as polymyositis. Although a direct causal relationship has not been established, shared immunopathological mechanisms are postulated, such as immune dysfunction and a persistent inflammatory environment. There is a need to undertake additional research to explore the connection between HPN and inflammatory myopathies, emphasizing the importance of a multidisciplinary and personalized approach in these patients.