Contracture-dominant paraneoplastic neuromuscular syndrome following B1 thymoma resection: a case report expanding the spectrum of thymoma-associated autoimmunity

Background: Thymoma is strongly associated with paraneoplastic syndromes, notably myasthenia gravis, and more rarely with autoimmune myositis. Among these, contracture-dominant presentations have been only rarely reported and remain poorly characterized. Case Presentation: We describe a 77-year-old woman who developed progressive distal tendon contractures thirteen months after resection of a B1 thymoma. She tested positive for anti-acetylcholine receptor, anti-titin, and anti-ryanodine receptor antibodies. Electrophysiology initially suggested a neurogenic pattern, later revealed myopathic features. Magnetic resonance imaging showed diffuse muscle edema and fibrosis, while muscle biopsy revealed neurogenic changes with secondary myopathic features. Corticosteroids and intravenous immunoglobulin yielded no clinical improvement. Discussion and Conclusions: This case expands the spectrum of thymoma-associated paraneoplastic neuromuscular syndromes and suggests that, in some patients, progressive structural remodeling rather than active inflammation may predominate. Recognition of atypical contracture-predominant presentations may facilitate earlier diagnostic evaluation in patients with thymoma-associated autoantibodies, although therapeutic responsiveness may be variable and likely dependent on disease stage.