G.P.76

On the muscle pathology of juvenile dermatomyositis (JDM), the muscle fibers show necrosis often in a part of a muscle fascicle, but rare in large region. We present peculiar muscle pathological findings in three patients suggesting large muscle infarction extending several fascicles with inflammatory changes. We investigated if there were some similarities among the three cases in clinical characteristics and pathlogies. Patient 1, 2 year-old female visited a hospital in November 2012 because of persistent fever, fatigue, weight loss and striae exanthema after having a cold. Elevations of ESR, ferritin, sIL-2R, FDP, ALD, KL-6 and anti CADM-140 antibody were detected. Interstitial lung disease resistant to immune therapies was rapidly progressed and died from respiratory failure. She was diagnosed with JDM because of muscle fiber necrosis of large area with thicken wall of middle sized arteries. Patient 2, aged 4, female presented in November 2012 with fever, fatigue and arthralgia and muscular pain of lower legs. The levels of CK, ESR, sIL-2R and FDP were elevated, however specific autoantibody was not detected. She recovered by methylprednisolone pulse and methotrexate therapies. Patient 3, 4 year-old female, after two months from the first symptom of photophobia, she was diagnosed JDM in November of 2012 due to fever, skin manifestations and muscle weakness. Elevations of CK, ESR, slL-2R and FDP without any specific autoantibodies were found. Treatment of methylprednisolone pulse and methotrexate were not effective. Common features of the three cases were female infant, acute or subacute onset of 2012 winter and high levels of inflammation and vasculitis markers. We suspect that obstruction of blood flow due to vasculitis is the cause for the large infarction. Some kind of natural immune response, such as viral infection, could contribute to develop JDM of infant whose immunoresponse is immature.