Juvenile dermatomyositis is an uncommon autoimmune systemic connective tissue disease. Despite its low prevalence, it accounts for 85% of all idiopathic inflammatory myopathies in children, and incidence rates vary between 2 and 4 cases per 1 million children depending on the series.1 Clinically, juvenile dermatomyositis is characterized by muscle weakness and distinctive cutaneous manifestations, which tend to occur as the presenting symptom. On occasions, the disease may affect other organs, such as the gastrointestinal tract, the heart, the lungs, the kidneys, and the eyes.2 Other complications, such as lipotrophy and calcinosis, may appear in late stages of disease, but they have become less common since the introduction of early intensive treatment. Diagnosis of juvenile dermatomyositis has traditionally been based on the criteria published by Bohan and Peter in 1975, but muscle biopsy is gradually being replaced by muscle magnetic resonance imaging (MRI), which is a noninvasive procedure that offers high sensitivity and performs better than muscle biopsy in terms of false negatives as it is not affected by the patchy distribution of disease.3–5 In view of these advantages, several groups have proposed incorporating muscle MRI findings into diagnostic and follow-up criteria.1,5,6

We performed a retrospective chart review of patients diagnosed with juvenile dermatomyositis at our hospital between January 1999 and December 2015. Our aims were to assess disease course and complications in patients treated with early intensive therapy and to evaluate the use of MRI rather than biopsy for detecting muscle involvement.

We studied 5 patients (4 boys and 1 girl) with a mean age at diagnosis of 10.4 years (range, 8-12 years). Time to diagnosis ranged from 2 months to 3 years. All the patients developed the characteristic cutaneous manifestations first. These preceded the onset of muscle involvement by periods ranging from 2 weeks to 3 years. The shortest time to diagnosis was observed in the 2 patients who presented with skin complaints (patients #2 and #4). The physical examination revealed Gottron papules and malar rash in patient #2 and Gottron papules, heliotrope erythema, and psoriasiform plaques on the scalp in #patient 4 (Table 1). The presenting manifestation in the other 3 patients was muscle weakness. All the patients had cutaneous manifestations, the most common of which were Gottron papules/the Gottron sign (present in 5/5 patients), heliotrope erythema (4/5), malar rash (4/5) and periungual telangiectasias (3/5) (Table 1).

The 5 patients had proximal muscle weakness, elevated levels of 1 or more muscle enzymes (alanine aminotransferase, aspartate aminotransferase, creatine kinase, aldolase), and muscle MRI findings consistent with myositis in the upper and lower limbs (Fig. 1). The electromyogram, performed in 4 patients, showed a myogenic pattern in the biceps and/or quadriceps. Two patients had positive antinuclear antibodies with low titers (1/160). None of the patients underwent muscle biopsy and a skin biopsy was performed in all cases (Table 1).

Figure 1.

Magnetic resonance imaging (MRI) findings. A, Patient #1. Whole-body muscle MRI. Increased intensity in STIR (short tau inversion recovery) sequence of buttock region and vastus lateralis, consistent with muscle edema, a sign of muscle inflammation. Integration of this finding confirmed the diagnosis of juvenile dermatomyositis. B, Patient #4. MRI of shoulder muscle. Increased signal from right deltoids and fascia in association with a small quantity of liquid in the subacromial bursa. C, patient #5. Whole-body muscle MRI after initiation of treatment. Note the hypointense calcinosis cutis plaque in the right low lumbar region (*).

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The starting treatment in 3 patients consisted of oral systemic corticosteroids 1mg/kg/d or intravenous corticosteroids at two 500-mg pulses combined with oral methotrexate 15mg/wk and hydroxychloroquine 200mg/d. Another patient was treated with oral prednisone 1mg/kg/d combined with ciclosporin and 6 boluses of intravenous immunoglobulin (IVIG). The last patient, who had mild muscle involvement, was treated with oral methotrexate 15mg and hydroxychloroquine 200mg combined with topical corticosteroids and tacrolimus. No systemic corticosteroids were administered. Four patients relapsed during follow-up and received different treatments (Table 2). Four patients are currently asymptomatic. Two are not receiving any treatment, 1 is receiving subcutaneous methotrexate 15mg/wk and hydroxychloroquine 200mg/d, and the other is receiving once-daily hydroxychloroquine 200mg as monotherapy (Table 3). None of the patients developed serious complications or organ involvement and just 1 developed calcinosis cutis in the form of a single plaque in the lumbar region 3 years after diagnosis.

We have presented 5 cases of juvenile dermatomyositis with cutaneous and muscle manifestations but no involvement of the visceral organs. The ratio of male to female patients was 4:1. This rate contrasts with reports of higher proportions of girls in larger series.1,2,7,8 The mean age at diagnosis was 10.4 years and the mean time to diagnosis was 11.25 months. These figures are similar to those described in the literature2,7,8 and indicate that diagnosis is often delayed in patients with juvenile dermatomyositis.

Diagnosis was established in all 5 patients on the basis of cutaneous and/or muscle involvement, elevated levels of 1 of more muscle enzymes, an electromyogram showing a myogenic pattern, and abnormal muscle MRI findings. A muscle biopsy was not needed in any of the cases. While not pathognomonic, edema in T1- and STIR (short tau inversion recovery) MRI sequences has been described as a specific feature of idiopathic inflammatory myopathies and juvenile dermatomyositis. Barsotti et al.9 reported that muscle edema had a sensitivity of 92.3% and a specificity of 83.3% for the diagnosis of inflammatory myopathies. Degree of edema on the MRI has also been found to correlate with levels of disease activity.3,5,9 The pelvis offers the greatest yield in muscle MRI, followed by the buttocks, the vastus medialis and lateralis, and the shoulders, thorax, and neck.5 Several authors have called for the use of whole-body MRI as the imaging test of choice because early involvement of the muscle in the above locations may not be clinically detectable.3,9 Detection of muscle edema by whole-body MRI in these and other locations would enable the early detection of asymptomatic disease, even in patients without elevated muscle enzymes or with a negative muscle biopsy result.3,5

Muscle biopsy can produce false-negative results in juvenile dermatomyositis due to the patchy distribution of disease. Muscle MRI, by contrast, examines the entire muscle area. It, therefore, offers greater sensitivity and, where necessary, can help in the selection of an appropriate muscle biopsy site.3,9 It also has high sensitivity for the detection of recurrence during follow-up, as it can show signs of disease activity in patients with normal muscle enzyme levels.4

Like other authors,1,3,9–12 we believe that muscle MRI is a valuable diagnostic and follow-up tool for juvenile dermatomyositis. It is safe, sensitive, and noninvasive and can be used instead of muscle biopsy in most patients. Several authors have proposed using muscle MRI as an additional diagnostic tool for juvenile dermatomyositis and the procedure is currently used by different working groups to evaluate and monitor inflammatory myopathies.1,3,4,9,12

Four of the 5 patients in our series showed excellent progress over a follow-up period of 4 to 12 years, and they are all currently asymptomatic and free of sequelae. The fifth patient was diagnosed and treated at a hospital in Ecuador for 3 years before being referred to our hospital with calcinosis cutis presenting as a small plaque. The plaque probably developed because the patient did not receive early aggressive treatment. Calcinosis has been linked to the presence of persistent inflammatory activity, and many authors have shown that early initiation of intensive treatment can prevent later complications.7,8,13

Although the prognosis of juvenile dermatomyositis has improved, early initiation of aggressive treatment and long-term follow up are still necessary as the disease runs an unpredictable course.

We have presented 5 cases of juvenile dermatomyositis, 4 of which were associated with excellent outcomes. These favorable results are consistent with reports in the literature and are probably thanks to the early initiation of intensive therapy.1,6,8,11,14 Just 1 patient developed calcinosis cutis and this was possibly due to late initiation of nonaggressive therapy.

Dermatologists have an important role in diagnosing juvenile dermatomyositis15 and muscle MRI is a safe, sensitive, noninvasive test for detecting and monitoring muscle involvement.

The authors declare that they have no conflicts of interest.