Angioedema-like presentation as the presenting finding of juvenile myositis and juvenile dermatomyositis in 2 patients.

Background: Juvenile dermatomyositis (JDM) is the most common subtype of idiopathic inflammatory myopathies in childhood. Gottron's papules, shawl sign, periorbital heliotrope rash, and periungual telengiectasis are characteristic skin findings of the disease. Besides characteristic skin involvement, some other skin findings, such as angioedema, may be seen prior or in the course of the disease. The presence of angioedema in JDM is emphasized in this report.

Case Presentations: We present 2 unrelated girls, aged 2 (case 1) and 12 years (case 2), who had developed symmetrical weakness in the proximal muscles, muscle pain, elevated muscle enzymes and angioedema. Both cases had abnormal muscle magnetic resonance imaging findings, suggestive of inflammatory myositis. Muscle biopsy was performed only in case 1, and major histocompatibility complex-1 expression on myofibers was shown consistent with JDM. Cases were diagnosed as probable and definite JDM, respectively. Angioedema was prominent, particularly in the lips and extremities of both cases, without laboratory evidence of C1 inhibitor deficiency or capillary leak syndrome, and absence of family history. Mast cell-mediated, acquired angioedema was the most likely diagnosis. In both cases, skin and muscle findings improved significantly with steroid treatment.

Conclusion: We suggest that angioedema may be among the characteristic skin findings in JDM, and may be included in subsequent definitions.