Pediatric emergency medicine trisk 2972 2972
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investigation. At this time, MSAs are of greatest utility in cases with atypical features,
for example in those without the characteristic rash or with features of an overlap
syndrome.
FIGURE 101.5 Gottron papules in juvenile dermatomyositis (JDM). (Courtesy of Lisa Rider, MD.)
Because JDM is a microangiopathic process, active disease is also characterized by
elevated levels of von Willebrand factor antigen (vWF:Ag), which is released by
damaged endothelial cells. In contrast, evidence of systemic inflammation may be
absent, and acute-phase markers (including ESR and CRP) and CBCs are typically
normal. MRI of the bilateral thighs may be the most sensitive method of documenting
muscle inflammation ( Fig. 101.4 ). Muscle biopsy can elucidate the diagnosis;
however, the diagnosis is more often made without it.
Evidence of cardiac involvement should also be sought, particularly with an EKG
and an echocardiogram. Serologic markers of myocardial involvement are unreliable
because both the CK-MB fraction and the troponin level are elevated in JDM due to
myoblast proliferation in skeletal muscles.
Management
General Management
The primary goal of therapy is to aggressively control muscle inflammation. The more
rapidly markers of myocyte damage such as CK and aldolase can be normalized, the
lower the chance that acute and chronic complications will occur. Thus, virtually all
children with clinical or biochemical evidence of muscle inflammation begin treatment
with pulsed doses of IV methylprednisolone (30 mg/kg, maximum 1.5 g) infused over
1 to 2 hours. Oral prednisone is then started at a dose of 1 to 2 mg/kg/day. If muscle
