Indian Pediatrics 2002; 39:931-935
Outcome in Juvenile Dermatomyositis
Juvenile dermatomyositis (JDM) is a rare multisystem disorder, primarily affecting the striated muscles and the skin. It constitutes about 2% of new diagnoses in a pediatric rheumatology clinic(1). It differs from adult dermatomyositis by the presence of vasculitis and ectopic calcification. In severe cases, death may occur due to respiratory failure, myocarditis or gastrointenstinal hemorrhage. Early diagnosis improves outcome and may prevent complications.
Previous studies from India(1,2) have reported a low prevalence or absence of calcinosis and a favorable outcome. We present a retrospective study of such patients followed up at our center over a period of 12 years.
Subjects and Methods
All patients of JDM (Bohan and Peter criteria)(3) seen in our clinic between 1989 and June 2001 were included. Data on the age of onset, duration of symptoms, clinical features, treatment and outcome were retrieved from the case records. All patients received prednisolone (1-2 mg/kg), with gradual tapering over the next year depending on the clinical response. Additionally, methotrexate (10 mg/m2/week) or azathioprine (2-4 mg/kg/day) was given to patients with partial response at 6-8 weeks treatment with steroids, those with steroid side effects, or severe disease. Cyclosporine and intravenous immunoglobulin were used in refractory cases. The response to therapy was graded as complete remission (normal muscle power, normal enzymes, no systemic features), partial remission (at least 1 grade improvement in muscle power), or no response.
Of 19 patients 12 were boys. The median age at diagnosis was 12 years (range 2.5-16 years) and duration of disease prior to diagnosis was 12 months (range 2-96 months).
Proximal muscle weakness was seen in all cases. Neck muscle weakness, predominantly of flexor muscles was seen in 14, pharyngeal muscle involvement in 5 and respiratory muscle involvement in 3 patients. The classical heliotrope rash was present in 9 patients, Gottron’s rash in 8, palpable purpura in 2 and diffuse erythema in one. Myocarditis with dilated cardiomyopathy and gastrointestinal bleeding were seen in one patient each and interstitial lung disease in 2 patients (Table I).
Elevated serum creatine phosphokinase levels (>192 IU) were present in 13 patients whereas electromyography was abnormal in all 19 patients. Anemia and elevated ESR were common. Antinuclear antibody was positive in 2 patients. Muscle biopsy done in 6 patients showed features suggestive of dermatomyositis.
All patients received prednisolone except one who was diagnosed to have JDM 8 years after the onset of symptoms and the muscle biopsy revealed only peri-fascicular atrophy without inflammation. Methotrexate was used in 13 and azathioprine in 3 patients. One patient received intravenous immunoglobulin since she had no response to treatment with corticosteroids and methotrexate.
Median follow-up period was 12 months (range 2-96 months). At last follow up, complete remission was seen in 8 patients (42.1%), partial remission in 8 (42.1%) and no response in 2 patients. One patient died of respiratory paralysis. Patient number 4 was diagnosed elsewhere at the age of 13 years and was in complete remission when first seen at our center. In the last 8 years, this patient had two relapses, the first responding to treatment with methotrexate and cortiocosteroids. The second relapse was treated with azathioprine and corticosteroids. One patient showed complete remission but her rash persists.
Complications included calcinosis (Fig.1) in 5 patients, contractures in 2, pulmonary tuberculosis in 4, steroid induced hypertension in 1 and pyogenic infections in 4 patients. The median duration of disease prior to diagnosis in patients with calcinosis was 10 months, which was not different from those without it (median 12 months).
Table I-Clinical Features at Presentation and Outcome
ILD - Interstitial lung disease, GI bleed - Gastrointestinal bleeding, DCMP - Dilated cardiomyopathy, CR, PR and NR - complete, partial and no response
Our cohort differs from other published from India in the following aspects: longer disease duration prior to diagnosis, more severe disease with involvement of neck and pharyngeal muscles, presence of calcinosis, arthritis, interstitial lung disease and gastrointestinal bleeding and low prevalence of antinuclear antibodies. The longer disease duration and more severe disease are probably related to referral bias to tertiary care centers.
Our patients had a slight male preponderance similar to that reported from Chandigarh(2) and Japan(4) but different from that elsewhere(1,5). The prevalence of antinuclear antibodies was low and similar to that reported by Singh, et al.(2) but different from that reported elsewhere(6). This cannot be explained by a difference in technique as a similar technique i.e., indirect immuno-fluorescence on HEp2 cells was used for the diagnosis.
Eighty percent of our patients showed a satisfactory response to therapy, as reported in other series(1,2). However, almost three-fourths required use of additional immunosuppressives other than corticosteroids. Persistence of rash despite improvement in muscle weakness has been reported in 40% of cases(7), as was seen in one of our patients.
The disease course in JDM may be monocyclic, polycyclic or continuous. Only 2 of our patients (patient number 4,10) have had relapses, most having a monocyclic or chronic continuous course. Relapse in a child with an apparent monocyclic course is uncommon as was observed in one patient after 12 years. No predictors for the course of disease could be identified at the onset of symptoms. Significant morbidity in the form of recurrent pyogenic infections, tuberculosis, calcinosis and contractures were seen in our cases, probably due to use of immunosuppressive agents and late institution of therapy(7).
Calcinosis, the most specific complication of JDM has been reported in 30-70% cases(8,9). Previous studies from India have either not reported or reported a low prevalence of this complication(1,2), probably due to short follow-up. Calcinosis shows a predilection for sites of repeated microtrauma (elbows, knees, flexor surfaces of fingers, buttocks). The reasons implicated for development of calcinosis are a delay in initiation of treatment, polycyclic or unremitting disease course, local trauma and the use of lower doses of corticosteroids(10). Calcinosis is resistant to most therapies including warfarin, ethidronate, probenecid, diltiazem, aluminum hydroxide and lithotripsy(10,11).
Contributors: VC and AW collected the data and wrote the manuscript. AA and RNM planned the study and provided critical inputs to the manuscript. RNM will act as a guarantor for the manuscript.
Competing interests: None stated.