Juvenile Dermatomyositis: Advances in Pathogenesis, Assessment, and Management
Authors: Leung Alexander K.C. , Lam Joseph M. , Alobaida Saud , Leong Kin F. , Wong Alex H.C. 
Published: April 2021

Background:

Juvenile dermatomyositis is the most common inflammatory myopathy in the
pediatric age group and a major cause of mortality and morbidity in individuals with childhood rheumatic
diseases. Mounting evidence suggests that early diagnosis and timely aggressive treatment are associated
with better outcomes.

Objective:

The purpose of this article is to provide readers with an update on the evaluation, diagnosis,
and the treatment of juvenile dermatomyositis.

Methods:

A PubMed search was performed in Clinical Queries using the key term “juvenile dermatomyositis”
in the search engine. The search strategy included meta-analyses, randomized controlled trials,
clinical trials, observational studies, and reviews. The search was restricted to English literature. The information
retrieved from the above search was used in the compilation of the present article.

Results:

Juvenile dermatomyositis is a chronic autoimmune inflammatory condition characterized by systemic
capillary vasculopathy that primarily affects the skin and muscles with possible involvement of
other organs. In 2017, the European League Against Rheumatism (EULAR) and the American College
of Rheumatology (ACR) developed diagnostic criteria for juvenile idiopathic inflammatory myopathies
and juvenile dermatomyositis. In the absence of muscle biopsies which are infrequently performed in
children, scores (in brackets) are assigned to four variables related to muscle weakness, three variables related
to skin manifestations, one variable related to other clinical manifestations, and two variables related
to laboratory measurements to discriminate idiopathic inflammatory myopathies from non-idiopathic
inflammatory myopathies as follows: objective symmetric weakness, usually progressive, of the proximal
upper extremities (0.7); objective symmetric weakness, usually progressive, of the proximal lower
extremities (0.8); neck flexors relatively weaker than neck extensors (1.9); leg proximal muscles relatively
weaker than distal muscles (0.9); heliotrope rash (3.1); Gottron papules (2.1); Gottron sign (3.3); dysphagia
or esophageal dysmotility (0.7); the presence of anti-Jo-1 autoantibody (3.9); and elevated serum
levels of muscle enzymes (1.3). In the absence of muscle biopsy, a definite diagnosis of idiopathic inflammatory
myopathy can be made if the total score is ≥7.5. Patients whose age at onset of symptoms is
less than 18 years and who meet the above criteria for idiopathic inflammatory myopathy and have a heliotrope
rash, Gottron papules or Gottron sign are deemed to have juvenile dermatomyositis. The mainstay
of therapy at the time of diagnosis is a high-dose corticosteroid (oral or intravenous) in combination
with methotrexate.

Conclusion:

For mild to moderate active muscle disease, early aggressive treatment with high-dose oral
prednisone alone or in combination with methotrexate is the cornerstone of management. Pulse intravenous
methylprednisolone is often preferred to oral prednisone in more severely affected patients, patients
who respond poorly to oral prednisone, and those with gastrointestinal vasculopathy. Other steroid-sparing
immunosuppressive agents such as cyclosporine and cyclophosphamide are reserved for patients
with contraindications or intolerance to methotrexate and for refractory cases, as the use of these agents
is associated with more adverse events. Various biological agents have been used in the treatment of juvenile
dermatomyositis. Data on their efficacy are limited, and their use in the treatment of juvenile dermatomyositis
is considered investigational.