Thymoma-associated stiff-person syndrome successfully treated with extended thymectomy: a case report

Stiff-person syndrome (SPS) is a rare autoimmune neurological disorder characterized by painful muscle stiffness and spasms. Paraneoplastic SPS associated with thymoma is rare. Here, we describe a rare case in which neurological symptoms improved after extended thymectomy.

A 60-year-old woman presented with progressive painful muscle spasms and gait disturbances affecting the lower extremities. Neurological imaging revealed no structural abnormalities; however, both serum and cerebrospinal fluid were positive for anti-glutamic acid decarboxylase (GAD) antibodies, leading to a diagnosis of SPS. Despite receiving immunotherapy and symptomatic treatment, the patient's neurological symptoms persisted. Contrast-enhanced chest computed tomography revealed a small anterior mediastinal tumor suspected to be a thymoma. Subsequently, bilateral thoracoscopic extended thymectomy was performed. Histopathological examination confirmed a WHO type B1 thymoma (Masaoka stage I), and her neurological symptoms gradually improved postoperatively. Two years after surgery, she was able to walk independently and climb stairs without assistance.

This case suggests that extended thymectomy may contribute to sustained neurological and functional improvement in selected patients with thymoma-associated SPS, even in the absence of normalization of the anti-GAD antibody titer.