A 42-year-old female was admitted to our hospital on October 1, 1990 because of one week history of back pain, weakness of her right lower extremity and sensory disturbance of her left lower extremity. Physical examination revealed swollen hands, Raynaud's phenomenon, sclerodactyly and heliotrope rash. The body temperature was 37.0 degrees C. Neurological findings included weakness in the right lower extremity, left hypalgesia and thermohypesthesia below Th4, hyperreflexia on the right lower extremity and right extensive plantar response. Laboratory data showed leucopenia (3,700/mm3) and hypergammaglobulinemia. Serological examination revealed antinuclear antibodies with a titer of 1:5120 (speckled pattern) and anti-RNP antibody with a titer of 1:32. Neither anti-DNA antibody nor anti-Sm antibody were detected. Serum C3 and C4 were normal. The cerebrospinal fluid (CSF) contained mononuclear cells of 5/mm3, protein 29 mg/dl and glucose 56 mg/dl. Queckenstedt test was negative. Treatment with prednisolone 60 mg daily was started. On the 8th day of therapy, she complained of a burning sensation in the back, then paraplegia and urinary retention developed. MRI examination showed a high intensity area of the spinal cord at the right Th4 on T2-weighted images. Next day the treatment with 1000-mg intravenous daily pulse of methylprednisolone for 3 days was started, followed by prednisolone 40 mg daily. After this pulse therapy, the CSF contained mononuclear cells of 52/mm3, protein 34 mg/dl, glucose 67 mg/dl and IgG 7.6 mg/dl. Her neurological manifestation gradually improved and at six weeks after the pulse therapy neurological examination revealed no abnormality except for painful tonic spasm. Prednisolone was slowly tapered to 15 mg daily.(ABSTRACT TRUNCATED AT 250 WORDS)