Dermatomyositis

Key Points
Connective-tissue disease
Causes inflammation of muscle and skin
Muscle weakness
Purple-red skin rash, often involving the eyelids

Dermatomyositis is an autoimmune disease with inflammation of the skin and muscle tissue. People who suffer from Dermatomyositis may experience muscle weakness, which may appear suddenly or develop slowly over weeks or months. Sufferers may have difficulty raising their arms over their head, rising from a sitting position, or climbing stairs. The rash may appear over the face, knuckles, neck, shoulders, upper chest, and back.

It is an uncommon to rare disease. It is usually chronic, however periods of spontaneous remission may occur. Treatment will also remedy muscle weakness and improve rash.

Causes include a genetic predisposition, autoimmunity defects, or an underlying cancer (especially in the elderly). Certain drugs may also trigger Dermatomyositis, such as Hydroxyurea, Penicillamine, Statins, Quinidine, and others. Juvenile Dermatomyositis occurs in children less than 18 years of age. In addition to the typical rash, children usually have hard white bumps of calcinosis in their skin. Juvenile DM is not associated with malignancy in most cases.

Differential Diagnosis (Other conditions with similar appearance)
CREST Syndrome
Parapsoriasis
Lupus
Sarcoidosis
Tinea Corporis
Morphea

Diagnosis
Key Points
Blood test and skin biopsy

Diagnosis is determined by blood tests, which are given to determine raised levels of circulating muscle enzymes and autoantibodies. Skin biopsies of the rash and/or the affected muscles are also taken. In some cases, Electromyography (EMG) testing or a Magnetic Resonance Imaging (MRI) scan of muscles is appropriate.

Treatment
Oral corticosteroids such as prednisone
Immunosuppressive or cytotoxic drugs
Diltiazem or Colchicine
Hydroxychloroquine
Avoid excessive sun
*Bedrest for inflammation

Treatment is given to control the skin and muscle disease. An oral corticosteroid (Prednisone) is the most frequent form of treatment, which is given to control inflammation. Immunosuppressive or cytotoxic drugs (Methotrexate, Azathioprine, Cyclophosphamide, Cyclosporin, Mycophenolate) may also be used. In addition, other measures include the use of diltiazem or Colchicine to reduce calcinosis. Hydroxychloroquine is effective for reducing photosensitive rash in some patients. Patients should additionally avoid exposure to the sun and/or use sunscreen because the rash is often worsened by sunlight.

Treatment for many patients is lifelong, although remission occurs in a small percentage of patients. Workup should include evaluation for malignancy in all adult patients newly diagnosed with Dermatomyositis, particularly a CA-125 level for female patients.