Stiff person syndrome (SPS) is a rare disorder of the central nervous system characterised by progressive fluctuating rigidity and painful spasms of the body musculature. We describe a patient with SPS with positive glutamic acid decarboxylase (GAD) antibodies who developed diplopia. Thymoma was detected by computed tomography (CT), and after thymectomy his symptoms improved. One month after thymectomy, he tested positive for antiacetylcholine receptor (AchR) antibodies.

Case report

A 45 year old man presented with a four week history of back pain and stiffness of his trunk causing difficulty in bending forward and turning over while lying down, which he attributed to a minor injury sustained while playing squash. He later developed asymmetrical stiffness of the legs and difficulty walking. His past medical history was notable for an episode of dysphagia (two weeks’ duration) associated with heartburn six months ago; a gastroenterological evaluation and an endoscopy at that time were normal. He recovered spontaneously and there was no recurrence.

On examination his mental status, speech, and cranial nerves were normal. He had exaggerated lumbar lordosis. Neurological examination showed normal bulk with increased tone of the flexors and extensors of the knee and ankles. Power and coordination were normal, deep tendon reflexes were brisk, but he had flexor plantar responses. There was no evidence of fatigable …