[A case report of steroid-responsive progressive encephalomyelitis with rigidity showing muscle stiffness limited to the upper body].

A 37-year-old female presented with progressive encephalomyelitis with rigidity for a period of about three months. Spasms began with several minutes of paroxysmal painful muscle stiffness in the left upper limb, followed by pain and muscle spasms in the upper limbs, shoulders, neck and back. The paroxysmal painful spasms were easily evoked by light touches and startling. The patient had contracture in the upper limbs and difficulty in relaxing the muscles. She also developed brain stem signs such as left sixth nerve palsy. The serum antinuclear antibody was positive (1 : 160). The cerebrospinal fluid examination revealed mild pleocytosis and protein elevation. Brainstem MRI, cervical MRI, and electroencephalography were normal. Surface electromyography in the arm and neck muscles showed continuous motor unit discharge elicited by passive movement of the right arm. Diazepam and baclofen were minimally beneficial. After treatment with intravenous injection of high-dose methylprednisolone and sequential oral prednisolone administration, the patient showed substantial improvement. This disorder may be part of a clinical spectrum that has an underlying autoimmune basis.