Clinical And Prognosis Analysis Of 53 Children With Dermatomyositis Or Polymyositis

Aim: To investigate the clinical manifestations, treatment regimen and prognosis of children with juvenile dermatomyositis(JDM) or juvenile polymyositis(JPM).Materials and Methods: The clinical manifestations, treatment and prognosis of 53 children with JDM or JPM admitted from Jan.1998 to Dec.2007 were analyzed retrospectively. The prognosis of a part of the patients was followed up through letter or telephone. 53 children were devided into two groups according to their diagnosis.Results: (1) Among the 53 cases studied, 37 were JDM, 16 were JPM. The ratio of JDM to JPM was 2.3 to 1. The ratio of boys to girls was 1 to 1.2. The average age of 53 children at onset was 6.9 years. No significant difference of gender and age between JDM and JPM. (2) 26.4%(14/53) children with JDM or JPM had antecedent illness, which were mostly respiratory infectious disease before onset of symptoms. (3) Characteristic cutaneous eruption(16/37), fever(14/53), symmetrical proximal muscle weakness(11/53) were common first onset symptoms. (4) As a systemic symptom of JDM/JPM, 20 out of 53 had fever, 12 were low or moderate fever for a long time. (5) All of the 53 children had symmetrical proximal muscle weakness and/or myalgia. Frequency of muscle weakness of JDM and JDM was 86.5%(32/37) and 87.5%(14/16), seperately. Frequency of myalgia of JDM and JPM was 59.5%(22/37) and 93.8%(15/16). No significant difference with muscle weakness between JDM and JPM(P>0.05), while, myalgia reach signifcant difference between JDM and JPM (χ2=6.32, P=0.01). (6) All of the cutaneous eruptions were active lesion, without damage lesion. The most appeared features were Heliotrope rash, Gottron's papules and sign with the frequency of 81.1%(30/37) and 48.6%(18/37). (7) Elevated muscle enzymes were noted in both JDM and JPM. The frequency of presence of elevated HBDH, LDH, CK and AST was 90.6%, 94.3%, 56.6% and 64.2%, respectively. Of the 53 cases, sensitivity between CK and LDH(χ2=20.39, P<0.05), AST and LDH(χ2=9.64, P<0.05), CK and HBDH(χ2=15.73, P<0.05) reach statistical difference. No significant difference of the sensitivity between CK and AST, HBDH and LDH. The sensitivity of HBDH between JDM and JPM reach significant difference(χ2=4.15, P=0.04). (8) Of 53 cases, the sensitivity between Erythrocyte sedimentation rate(ESR) and C-reactive protein(CRP) do not reach significant difference(P=0.46). (9) Electromyography(EMG) revealed typical change of myopathic type. EMG abnormalities mainly showed decreased motor action potential duration 60.0%(24/40) and amplitude 50.0%(20/40), increased spontaneous potential 25%(10/40). (10) 9 out of 12 had typical histopathological findings in the muscle include swelling of the muscle fibers with degeneration, perifascular atrophy, intersitial mononuclear infiltrates, capillary obliteration of the lumen. (11) Clinical and functional outcomes have been much improved. With the initiation of corticosteroid therapy, systemic manifesitations and myalgia improved immediately, muscle weakness and cutaneous eruptions disappeared gradually, level of muscle enzymes reached normal. None had interstitial lung disease(ILD) and tumor.Conlusions: (1) Prevalence of JDM/JPM is more in girls than boys. More cases are arises during school age. (2) Common antecedent illness is respiratory infectious disease. (3) At the onset of JDM/JPM, typical cutaneous eruptions, muscle weakness and systemic manifestations are easily recognized, should be given more attention and differentiate with other rheumatoid dieases or myopathies. (4) Symmetrical muscle weakness of proximal limbs is common in both JDM and JPM, while the latter is tend to have myalgia. (5) All of the JDM children have activity lesions, Heliotrope rash has the highest ratio. (6) Muscle enzymes is sensitive, HBDH and LDH have the highest sensitivity. Sensitivity of HBDH in JDM is higher than in JPM. (7) ESR and CRP have equal sensitivity in JDM/JPM. (8) Typical myopathic type is common in JDM/JPM, few EMG finding can be atypical. EMG finding could have early diagnostic significance. (9) Histopathological changes as one of the main standards of JDM/JPM involves of vascular, muscles fibers and inflammatory cells et al. (10) Master of JDM and JPM clinical features in particular the early clinical characteristics is important for early diagnosis. Reasonable treatment is the key for improving prognosis. With regular follow up, few children will develop malignant tumor or intersitial lung disease(ILD), most children will have improve.