Several cases of classic dermatomyositis progress to postmyopathic DM

Nearly half of patients with classic dermatomyositis (DM) develop into postmyopathic (PM)DM, according to a study. Many of them continue to suffer from muscle disease or have moderate or severe skin disease.

On the other hand, patients with clinically amyopathic (CA)DM are at low risk of progressing to muscle disease, “with the extent of skin disease as a potential predictive factor,” the authors said.

This study sought to track and describe classic DM and CADM patients who had changes in disease presentation. The author retrospectively reviewed prospectively collected data on 269 patients with DM from a longitudinal database.

Of the patients, 51 percent had classic DM and 49 percent CADM. Among those with classic DM, 40 percent progressed to PMDM. PMDM patients had lower median Cutaneous Dermatomyositis Disease Area and Severity Index activity (CDASI-A) score than those with classic DM (13.0 vs 16.0), but 45 percent of PMDM patients had CDASI-A scores >14.

A few patients with CADM (5 percent) developed muscle involvement. Others who developed muscle symptoms, compared with CADM patients, had milder skin disease before subtype conversion (median CDASI-A 12.0 vs 16.0) and at subtype conversion (median CDASI-A 9.0 vs 16.0).

The study was limited by its retrospective and single-centre design.