ABSTRACT: The idiopathic inflammatory myopathies are a heterogeneous group of disorders; excluding conditions that mimic them during the initial patient evaluation is essential. Classification of dermatomyositis (DM) for a definitive diagnosis requires a characteristic rash and other criteria, such as proximal muscle weakness and muscle enzyme level elevation. DM often overlaps with other connective tissue diseases. A photosensitive rash often is the initial manifestation. Cardiac and pulmonary involvement may be life-threatening. Malignancies occur in up to 25% of cases. A detailed strength examination at every visit is important for assessing treatment response. Muscle biopsy is central in establishing the diagnosis. Physical therapy and occupational therapy should be started at diagnosis. Corticosteroids are the foundation of treatment. Most patients require corticosteroid-sparing medication.
(J Musculoskel Med. 2008;25:415-420, 444)
Dermatomyositis (DM) is one of the idiopathic inflammatory myopathies (IIMs), a heterogeneous group of disorders that involve proximal muscle weakness and nonsuppurative skeletal muscle inflammation. Others are polymyositis (PM) and inclusion body myositis (IBM). Excluding conditions that mimic the IIMs during the initial patient evaluation is essential.1 Not every patient who has myopathic weakness, elevated creatine kinase (CK) levels, and inflammatory muscle histology has DM or PM, and there is clinical and pathological overlap with myositis associated with collagen(Drug information on collagen) vascular diseases. In addition, other conditions that do not respond to immunosuppression (eg, muscular dystrophy, IBM, metabolic myopathies, and neuromuscular disorders) also may have these features.
If treatment of a patient with DM or PM is unsuccessful, the muscle biopsy should be reexamined or a second biopsy ordered to reassess the diagnosis. Elevated levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) in patients with nonspecific symptoms often direct attention to liver disease. These enzymes also are found in muscle; if levels are elevated, the CK level should be checked to evaluate for myositis. Although the CK level is helpful, the response to therapy is best appraised by monitoring muscle strength and function. "Treating" the CK level instead of the muscle weakness may lead to unnecessarily prolonged use of immunosuppressive medications and incorrect judgment about their efficacy.2
In this article, we offer a case report of a patient with DM. Then we review the key points of diagnosis and treatment.
A 39-year-old woman, in her eighth week of pregnancy, was admitted with myalgia, proximal muscle weakness, and a rash that had developed over the course of 1 week. She experienced aching pain that worsened with activity; thigh and proximal arm muscle fatigue and weakness began 3 days later. Then a mildly pruritic rash across the forehead, nose, and forearms developed. Her symptoms progressed rapidly, and within days she required assistance from 2 persons to rise from a chair; she also had difficulty walking, brushing her teeth, bringing objects to her mouth, and washing her hair. She felt feverish (temperature, 37.2°C [99°F]).
One year earlier, about 3 to 4 weeks into a pregnancy, the patient had experienced similar proximal myalgia and very mild weakness without rash. The symptoms had resolved in 2 weeks without medical attention. This pregnancy ended in miscarriage at 10 weeks.
The patient smoked cigarettes, 1 pack a day for 15 years, but she denied alcohol(Drug information on alcohol) or illicit drug use. The only medication she took was a prenatal vitamin.