Dermatomyositis and polymyositis associated with malignancy: a 21-year retrospective study.

OBJECTIVE: To analyze clinical and laboratory data of patients diagnosed with dermato- or polymyositis between 1985 and 2006, retrospectively, with particular emphasis on association with malignant diseases.
METHODS: A thorough clinical assessment was performed on the immunological features and therapeutic responses, as well as survival data. In the case of 155 myositis patients, HLA haplotypes were also investigated.
RESULTS: Out of 309 patients with myositis in our database, malignant disease was found in 37 cases. Thirty patients had dermatomyositis (28.8%), and 7 had polymyositis. In 64.8% of the cases, the malignancy and myositis appeared within 1 year. The highest probability for tumor recognition was before 2 years and after 3 years of the diagnosis of myositis (28 cancer-associated myositis): most frequent was breast tumor, and adenocarcinoma was the predominant histological type. The skin lesions and diaphragmatic involvement were more severe; distal muscle weakness was conventional, along with proximal muscle weakness and frequent immobility. Creatine kinase and lactate dehydrogenase elevations were lower than in primary myositis, and when controlled 1 month after surgical treatment of the malignant disease, these values showed significant reduction. Tumor markers did not predict the occult tumors. We found no correlation between the presence of tumor and DRB1-0301 and -01 alleles.
CONCLUSION: In patients with tumor-associated myositis, it was more frequently necessary to administer other immunosuppressive drugs along with glucocorticoids. The successful treatment of the underlying malignant disease improved the clinical course of myositis. The overall survival rate was considerably worse when compared to other forms of myositis.