Methotrexate, supplemented by short-term use of systemic corticosteroids, is the cornerstone of therapy for JDM. Initial treatment with pulse intravenous methylprednisolone is followed by several months of tapering doses of oral prednisone. Early institution of methotrexate significantly decreases the duration of corticosteroid use and its associated toxicities. In severe or refractory cases, it may be necessary to use cyclosporine or cyclophosphamide. Intravenous immunoglobulin is useful as adjunctive therapy. Hydroxychloroquine or dapsone has been used for the skin manifestations. These drugs do not significantly affect the muscle disease. Exposure to the sun worsens the cutaneous manifestations and exacerbates the muscle disease; sunlight may lead to flare. Patients should be advised to wear sun block and refrain from prolonged sun exposure. Accordingly supplementation with calcium and active forms of vitamin D is also indicated.
The most serious complication of JDM is the development of calcinosis. Dystrophic calcification can occur in the skin and soft tissues in any area of the body; it ranges from mild to extensive (calcinosis universalis). Although it is difficult to predict who will develop calcinosis, it occurs more commonly in children with cutaneous vasculitis, prolonged disease activity, or delays in onset of therapy. Patients with JDM who develop vasculitis also are at risk for gastrointestinal perforation and gastrointestinal bleeding. JDM has been associated with lipoatrophy and insulin resistance, which can progress to type 2 diabetes. Control of insulin resistance frequently leads to improvement in muscle disease in these patients.
The outcome of JDM depends greatly on the extent of muscle disease and the time between disease onset and initiation of therapy. JDM follows one of three clinical courses: a monophasic course, in which patients are treated and improve without significant sequelae; a chronic recurrent course; and a chronic progressive course marked by poor response to therapy and resulting loss of function. Patients who ultimately develop calcinosis are at risk for chronic loss of mobility, depending on the extent of calcium deposition. The association of dermatomyositis with malignancy seen in adults does not occur in children.
Growing pains, or benign musculoskeletal pain syndrome, occur in 10% to 20% of school-age children. The peak age range is 3 to 7 years; the syndrome seems to be more common in boys than girls. There is no known etiology, although there seems to be a familial predisposition.
Children with growing pains complain of deep, crampy pain in the calves and thighs. It most typically occurs in the evening or as nocturnal pain that occasionally can waken the child from sleep. Growing pains tend to be more common in children who are extremely active; bouts are exacerbated by increased physical activity. The physical examination is unremarkable, with no evidence of arthritis or muscular tenderness or weakness. Laboratory studies or x-rays, if performed, are normal.
The diagnosis of growing pains is based on a typical history and a normal physical examination. Hypermobility excludes the diagnosis. It is important to consider leukemia as a cause of nocturnal leg pain in children of this age group, so it is prudent to document a normal complete blood count.
The treatment of growing pains consists of reassurance and a regular bedtime ritual of stretching and relaxation. The pain can be relieved by massage. Some patients may benefit from a nighttime dose of acetaminophen or an analgesic dose of a nonsteroidal anti-inflammatory drug (NSAID). Occasionally nocturnal awakening has been of long duration, leading to disruptive behavior patterns. In these cases, intervention must be aimed at decreasing the secondary gain associated with nighttime parental attention and should focus on sleep hygiene. Other than the negative behavioral patterns that can occur, there are no significant complications. Growing pains are not associated with other illnesses and resolve over time.
Figure 92-1 Hyperextension of the knees, an example of hypermobility.