A 52-year-old woman was admitted to our hospital with
muscle pain and an elevated
creatine kinase level. She had experienced wrist
pain at onset seven years ago. The initial possible diagnoses were
rheumatoid arthritis and
adult-onset Still disease. The patient received
corticosteroid and
immunosuppressant therapy but experienced deterioration of symptoms. The symptoms of
muscle pain and mild
creatine kinase elevation emerged four years prior to her visit. Further elevation of
creatine kinase was observed for three months before her visit despite adjusting the
immunosuppressant dose. On admission, she presented with muscle moderate weakness of the trunk and extremities and
pain of the shoulder and medial thigh muscles. Elevation of muscle
enzymes and inflammatory response were also detected, and the anti-PL7 antibody was positive. Muscle biopsy from biceps brachii revealed necrotizing
myopathy with necrotic and regenerated muscle fibers. The final diagnosis was anti-PL7 antibody positive
myositis. The patient was treated with a higher dose of
prednisolone and an adequate dose of
tacrolimus. Following this treatment, the symptoms were improved. Anti-ARS (aminoacyl t-
RNA synthetase)
antibodies such as anti-PL7 antibody are useful in diagnosis and for prognostic prediction. Further investigation of patients with anti-ARS
antibodies positive
myositis is required.