Extensive assessment critical to dispel 'ambiguity' mimics in juvenile dermatomyositis
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Juvenile dermatomyositis challenges rheumatologists to accurately assess not only the skin but also pulmonary and cardiac function in making a diagnosis, according to a speaker at the 2021 Rheumatology Nurses Society annual conference.
“Juvenile dermatomyositis is the most common inflammatory myopathy of childhood,” W. Blaine Lapin, MD, assistant professor at the University of Connecticut School of Medicine, told attendees.
The condition is a multisystemic autoimmune vasculopathy marked by proximal muscle weakness and rash with an average age of onset of 7 years. “This is characterized by a symmetric axial and proximal muscle weakness,” Lapin said.
Importantly, children experiencing these complications may have trouble climbing stairs or getting out of bed, according to Lapin.
Regarding the rash, Lapin noted that patients with JDM may have Gottron’s papules or heliotrope rash, malar erythema, linear extensor erythema and V- or shawl-sign rashes. There may be raised rashes over extensive surfaces, while the metacarpophalangeal or proximal interphalangeal joints may be impacted. “It can also be over the elbows or knees,” Lapin said.
A small vessel vasculopathy with dilated and tortuous periungual capillaries may be present. “In addition to skin and muscle involvement, gastrointestinal, pulmonary and cardiac systems may be affected,” he said.
Gastrointestinal complications may include perforations, gastric ulcers or constipation, while tachycardia is the most common cardiac complication.
Laboratory tests in the diagnosis of JDM should include a complete blood count, a comprehensive metabolic panel, creatinine kinase, lactate dehydrogenase, aldolase, erythrocyte sedimentation rate (ESR)/C-reactive protein, thyroid stimulating hormone, myositis-specific and myositis-associated autoantibodies and antinuclear antibodies. “About 70% of individuals have at least one autoantibody,” Lapin said. “Autoantibodies help describe certain phenotypes of JDM.”
To diagnose lung disease, a simple chest X-ray may be sufficient to start. A pulmonary test or a high-resolution chest CT scan with interstitial lung disease protocol may also be necessary. An MRI or muscle biopsy may be used to assess for myopathy, according to Lapin.
For clinicians making a differential diagnosis, Lapin suggested that there “may be some ambiguity based on presentation.” JDM may mimic or overlap with syndromes including polymyositis or amyopathic dermatomyositis.
Corticosteroids are the “hallmark” of JDM treatment, Lapin said. “They work well in up-front treatment [and] lead to improvement in function,” he said. Steroids may be administered in pulse dosing at first, followed by an “extensive course” of oral steroids. “Oral steroids can be administered with a slow taper, possibly as long as a year.”
Intravenous immunoglobulin, methotrexate, hydroxychloroquine, cyclosporine and rituximab (Rituxan, Genentech) have been used with some efficacy in this patient population, according to Lapin.
Regarding expected disease course, Lapin noted that clinicians may observe a “rule of thirds.” This means that one-third of patients will have a monocyclic course that will last for less than 2 years, followed by a permanent remission; one-third will have a polycyclic course marked by repeated flares and remissions; and one-third will have persistent disease that is difficult to control.
Favorable prognostic factors include a shorter delay to diagnosis, lower skin disease activity and early aggressive treatment. Patients at risk for a poor prognosis include those with a longer duration of untreated disease, higher baseline or persistent skin disease activity, the presence of subcutaneous edema on MRI at diagnosis or extensive myopathic and severe arthropathic changes on the initial muscle biopsy, according to Lapin.
If there is a final consideration for clinicians treating pediatric patients with JDM, it is the transition to adult care. “Parents may have increased worry,” he said. “The whole family may be impacted by this chronic illness. There is an importance on psychosocial support.”
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Lapin WB. Kids Grow Up: What You Need to Know About Juvenile Dermatomyositis (JDM) for Both Pediatrics and Adult Care. Presented at: Rheumatology Nurses Society annual conference; August 4-7, 2021 (virtual meeting).
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