Diagnosis: Dermatomyositis
Dermatomyositis is a systemic disease classified as a type of idiopathic inflammatory myopathy. Dermatomyositis is a rare disease but one that may present initially to the family physician. It affects people at any age but is more commonly seen among children or adults aged >40 years.
Dermatomyositis involves the skin as well as skeletal muscle. Its cause is unknown; however, among those aged >50 years, malignancy may be an underlying cause. Cancers most commonly associated with dermatomyositis include those of the breast, ovary, lung, and gastrointestinal tract.
Skin manifestations may precede, follow, or present simultaneously with muscle involvement. Patients often complain of having difficulty ascending stairs, rising from a seated position, and performing overhead activities such as combing their hair. Patients may or may not have muscle tenderness and atrophy. Patients can have cutaneous involvement for more than a year before developing muscle weakness.1
The dermatologic signs of dermatomyositis to watch for:
- Periorbital heliotrope erythema, usually associated with edema (FIGURE 1).
- Gottron’s papules—smooth, purple to red papules located over the knuckles, on the sides of the fingers, and sometimes on the elbows and knees. For adults, it is not uncommon to have plaques over the knuckles as opposed to the classic Gottron’s papules (FIGURE 3). In juvenile-onset dermatomyositis, distinct papules are much more evident upon presentation (FIGURE 4). Note that systemic lupus erythematosus (SLE) can present with a rash on the dorsum of the hands, but the rash spares the skin over the metacarpophalangeal and interphalangeal joints and affects the skin between the joints (FIGURE 5).
- Violaceous papular dermatitis with scale—may occur in localized areas, such as elbows and knees, or be diffusely distributed, starting off as a patchy erythema that coalesces and becomes slightly raised with scale. It tends to be confined to sun-exposed areas and worsens after sun exposure (FIGURE 2).
- Periungual erythema and telangiectasia—“moth-eaten” cuticles, a characteristic seen in other connective tissue diseases (FIGURE 6).1
FIGURE 4
Papules on knuckles
FIGURE 5
Sparing interphalangeal joints
FIGURE 6
Cuticles with erythema
