Polymyositis secondary to paroxysmal nocturnal hemoglobinuria (PNH). Case report.

Abstract

We present the case of a 35-year-old female 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, transvaginal bleeding, and desquamative skin lesions, progressing to septic shock, neurological compromise, 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 initiated, achieving initial partial improvement and adequate functional status without signs of polymyositis 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, such as immune dysfunction and a persistent inflammatory environment, are postulated.
There is a need for further research to explore the connection between PNH and inflammatory myopathies, emphasizing the importance of a multidisciplinary and personalized approach in these patients.

Introduction

HPN is a rare benign clonal disease caused by mutations in the PIGA gene, which affects the synthesis of the protein that anchors glycosylinositol phospholipids (GPI), responsible for anchoring protective cell membrane proteins such as CD59 and CD55, triggering uncontrolled complement activation(1).
HPN is characterized by anemia secondary to intravascular hemolysis, which increases the risk of atypical thrombotic events (suprahepatic, portal, mesenteric, inferior vena cava, central nervous system, dermal, and retinal). Hemoglobinuria, leukopenia, and/or thrombocytopenia are also present. The hemoglobin released into the circulation sequesters nitric oxide, causing peripheral vasoconstriction and symptoms such as dysphagia, erectile dysfunction, abdominal and chest pain, and profound asthenia, limiting daily activities(1,2).
We present the case of a patient with previously diagnosed PNH, with clinical symptoms of aplastic anemia, for which she was receiving specific immunosuppressive treatment (anti-thymocyte globulin). In addition, treatment with eculizumab had been ruled out due to low clonality in erythrocyte cells and low cellularity in erythrocyte cells (< 1%), and she developed a clinical picture consistent with polymyositis, confirmed by anatomopathological study.
Inflammatory manifestations such as aseptic meningitis, recurrent urticaria, and arthralgia have been observed in PIGA gene mutations(5).

Polymyositis is an acquired inflammatory myopathy characterized by progressive weakness of the proximal muscles. Although its etiology is unknown, it is frequently associated with autoimmune diseases(3).
While polymyositis mainly affects striated muscle, this systemic disease can compromise joints and internal organs such as the lungs. Patients experience symmetrical muscle weakness affecting the neck, shoulders, hips, and thighs, limiting daily activities such as lifting objects, getting up from a seated position, or climbing stairs. Other symptoms include fatigue, arthralgia, fever, hyporexia, and weight loss(3).

Wilches Meza a 2; Navarro J 1,2; Garcia Osorio A 2; Arenas López K 2; Martínez Guerrero G 3,4; García Torres C 3,4; González Torres E 4, Chaytili Gómez K 4; Cruz Carmona B 4.
1- Scientific Division Department, Bonnadona Prevenir Clinical Organization, Barranquilla, Atlántico. Colombia.
2- Department of Internal Medicine. Bonnadona Prevenir Clinical Organization, Barranquilla, Atlántico. Colombia.
3- Department of Epidemiology. Bonnadona Prevenir Clinical Organization, Barranquilla, Atlántico. Colombia.
4- Research Seedbed. Bonnadona Prevenir Clinical Organization, Barranquilla, Atlántico. Colombia.

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