Dermatomyositis with normal creatinine kinase: 3 cases report and review of the literatures

Abstract

Objective Elevated creatinine kinase (CK) is an important item in the diagnostic criteria of dermatomyositis.Dermatomyositis with normal serum CK is rare.The clinical diagnosis and treatment of the disease with be discussed through the analysis of 3 cases with normal CK and the review of relevant literatures. Methods Clinical data were retrospectively analyzed, including medical history, physical examination, serum CK, electromyography, and pathological data of muscle biopsy.The treatment was followed up for 1.0 to 2.5 years. Results All 3 male patients were 9 year, 8 years old, 1 year and 10 months old, respectively.The time from onset to diagnosis was 1 year and 9 months, 1 year, and 7 months, respectively.The first and most prominent symptom was symmetrical weakness.One of the patients had typical macula of dermatomyositis.Variable decrease of muscle strength and muscle tone was detected in all patients.Serum CK was normal in all 3 patients.Electromyography showed myogenic changes in 2 patients, while no abnormal change was detected in another patient.Muscle biopsy showed prominent perifascicular muscle fiber atrophy and inflammatory infiltrates confined to perimysium, which was the characteristic pathology of dermatomyositis.Typical pathologic manifestations were found from quadriceps femoris in patient 1, with nonspecific foundlings in previous gastrocnemius muscle biopsy.The treatment of corticosteroids in 2 recovered patients lasts for 2 years, while the disease relapsed in 1 patient with corticosteroids therapy for 1 year. Conclusions Serum level of CK may be normal in dermatomyositis patients with occult onset and long term courses.Early, sometimes multifocal muscle biopsy is helpful for the prevention of the miss or misdiagnosis of dermatomyositis.Corticosteroids are the first choice for the treatment of dermatomyositis, and sufficient course of therapy is important for good outcome. Key words: Dermatomyositis; Creatinine kinase; Muscle biopsy; Corticosteroids