Dermatomyositis (DM) is the most easily recognized of the inflammatory myopathies due
to its distinctive rash. This rash occurs as a patchy, dusky, reddish or lilac rash on the
eyelids, cheeks, and bridge of the nose, and on the back or upper chest, elbows, knees and
knuckles. Some people with dermatomyositis develop calcified nodules or hardened bumps
under the skin. The rash often precedes muscle weakness.
Muscle weakness usually develops over a period of weeks but may develop over months or
even days. The weakness initially affects those muscles closest to and within the trunk of
the body, including neck, hip, trunk, and shoulder muscles. Difficulty swallowing occurs
in at least one third of DM patients. Whereas less than 25% of adults report muscle pain,
more than 50% of children with DM complain of muscle pain and tenderness.
Dermatomyositis can occur at any age from childhood to adulthood and is more common in
females than males.