Dermatomyositis sine myositis: association with malignancy.

OBJECTIVE

To describe dermatomyositis (DM) sine myositis as a distinct diagnostic subclass of DM and the association with malignancy.

METHODS

This case series includes all patients presenting to our primary and tertiary care outpatient dermatology department with DM and DM sine myositis between 1986 and 1993. Seven patients were diagnosed with classic DM and 12 with DM sine myositis. We analyzed average age of onset, duration of followup, clinical course, and incidence of associated malignancy in the patients with classic DM and DM sine myositis.

RESULTS

No statistically significant differences were found in these 2 groups on examining age at onset and frequency of associated malignancy. Malignancy was diagnosed in 4 of 12 (25%) patients with DM sine myositis followed for a total of 50.8 patient-years (average followup 51 months) and in 2 of 7 (28%) patients with classic DM followed for a total of 20.6 patient-years (average followup 35 months).

CONCLUSION

Although these patients with DM are select and few, they demonstrate that DM sine myositis may be quite similar to classic DM. It may be said that like DM, DM sine myositis may represent a paraneoplastic syndrome. DM sine myositis should be added to the currently accepted polymyositis/dermatomyositis classification system, with appropriate emphasis on the potential association with malignancy.