Juvenile Dermatomyositis — Pediatric EM Morsels

We have previously discussed our “love” of rashes! Ok, maybe we are still lukewarm when it comes to skin eruptions, but we cannot deny the important clues that we may decipher from a good derm exam! This is especially true when we are facing the complaint of weakness and muscle pain. There are a lot of considerations on our list when we are pondering the child who complains of muscle weakness! Let’s take a moment heighten our awareness about one diagnosis that should be on that list – Juvenile Dermatomyositis:

Juvenile Dermatomyositis: Basics

Juvenile dermatomyositis (JDM) is an inflammatory myopathy with characteristic skin and muscle involvement
It’s rare, but it’s the most common idiopathic inflammatory myopathy of childhood (Sag, Huber)
JDM is a systemic illness that can lead to significant long-term morbidity and mortality:
- Inflammation in the heart, lungs, and other organ systems
- Early recognition and treatment is critical to improve long-term outcomes
The cornerstone of treatment is high-dose steroids and methotrexate, with other immunosuppressive agents as needed

Juvenile Dermatomyositis: Epidemiology and Pathogenesis

JDM affects approximately 3 per every 1 million children per year in the US (Sag, Huber)
It has a bimodal distribution: peaking ages 5 to 15 years, then again at 40 to 60 years (Sag, Huber)
It has a 2:1 female to male predominance (Barut, Feldman)
JDM can be secondary to underlying genetic predispositions (Feldman) or triggered by infections, other inflammatory conditions, and UV light exposure (Mainetti, Bogdanov)
- Many children diagnosed with JDM had a preceding respiratory or gastrointestinal illness in the 3 months prior to disease onset (Feldman)
- Common infectious triggers include influenza, enterovirus, echovirus, coxsackie virus, and parvovirus B19 (Maintetti, Bogdanov, Feldman)

Juvenile Dermatomyositis: Clinical Features

JDM classically presents with proximal muscle weakness and one or more characteristic skin finding (Bohan and Peter)
- The two most common skin findings are Grotton’s papules and a heliotrope rash. (Sag, Barut) [for images of rash – DermIS and DermNetNZ.
- Grotton’s papules are pathognomonic for JDM.
  - They are erythematous, sometimes raised, sometimes scaling lesions on the extensor surfaces of the fingers, often overlying the interphalangeal joints (Mainetti)
- A heliotrope rash is red or purple periorbital discoloration and edema (Mainetti)
JDM can also present with photodistrubution erythema.
- On the face, this can look like erythema of the forehead, cheeks, nasal bridge, and chin;
- On the rest of the body, this can present as erythema of the anterior chest, nape of the neck, shoulders, and backs of the upper arms/forearms (Mainetti)
Less common skin findings are “Mechanic’s Hands,” with irregular, thickened, and cracked cuticles; oral mucosal changes; and the “Holster Sign,” with erythema to the upper/lateral thigh (Cancarini, Mainetti)
Muscle involvement is typically proximal, symmetrical, and progressive.
- Present with pain and weakness in their shoulders/upper arms, hips, pelvis, and thighs.
- Difficulty climbing stairs, getting up from a chair, or brushing their hair (Mainetti, Sag)
Neck and diaphragm muscles can also be involved, leading to dysphagia or respiratory distress, but this is less common (Mainetti, Sag)
Skin lesions can sometimes present months to years before muscle symptoms (Mainetti)
As JDM progresses, patients can present with the sequela of inflammation to other organ systems.
- Respiratory distress from lung involvement
  - About 75% of children will have associated lung disease (Wienke)
- Heart failure from cardiac involvement
- Abdominal pain from gastrointestinal involvement

Juvenile Dermatomyositis: Differential

JDM shares many characteristics of other idiopathic inflammatory myopathies, including polymyositis, inclusion body myositis, focal nodular myositis, among others (Feldman)
Other autoimmune conditions can also have similar signs/symptoms, such as systemic lupus erythromatosus, systemic sclerosis, juvenile idiopathic arthritis, mixed connective tissue disease, and myasthenia gravis (Feldman)
Viral myositis and rhabdomyolysis should also be considered

Juvenile Dermatomyositis: Evaluation and Diagnosis

Classically, JDM was diagnosed clinically based on the presence of Grotton’s papules and/or heliotrope rash with one or more sign of muscle involvement (including muscle weakness, abnormal muscle enzymes, abnormal muscle biopsy, and abnormal muscle EMG) (Bohan and Peter)
Muscle enzymes can be elevated including creatine kinase, aldolase, AST, and ALT (Wienke); LDH is also elevated (Wienke)
- Lab abnormalities are less reliable in children as compared to adults with dermatomyositis (Wienke, Feldman)
JDM is associated with specific auto-antibodies, including anti-MDA5, anti-Mi2, anti-TIF 1, and anti-NXP 2 (Wienke, Feldman)
MRI can show inflammation and edema of the proximal muscles (Mainetti, Feldman)
Muscle and skin biopsies will show atrophy, inflammation, and lymphocyte infiltration, but are not always performed due to their invasive nature (Wienke, Feldman)
EMG might show changes to the electrical flow through muscles (Mainetti)

Dermatomyositis: Treatment

The cornerstone of treatment is high dose steroids and methotrexate (Kim)
- Steroid dosing recommendations vary
- Typically children receive IV methylprednisone (up to 1000mg/day) or oral prednisolone (1 mg/kg/day) (Mainetti, Sag)
Second-line immunosuppressive agents can be used for refractory cases, including azathioprine, mycophenolate, and cyclosporine (Sag, Kim)
IVIG is also used for refractory cases (Sag, Kim)
Rituximab and other biologic agents are sometimes considered (Kim)
Rheumatology should be involved early to help guide treatment and children will often require admission for IV therapies and rheumatology consult

Dermatomyositis: Prognosis

Morbidity and mortality is improved with earlier initiation of steroids (Feldman)
Prognosis varies, and is dependent on severity of initial presentation, initial response to treatment, as well as specific auto-antibodies (Kishi)
Most patients will have improvement or resolution of symptoms by two years (Sag) but time to steroid discontinuation and clinical response can be as long as 4 to 7 years (Sag, Kishi)
JDM is often chronic and relapsing
- ~1/2 of kids will have persistent weakness and functional limitations
- ~ 1/4 will relapse even after resolution (Sag, Ravelli)
Mortality estimates range from 1-3% even with treatment (Huber, Ravelli)
- Mortality is often from inflammation in other organ systems (Feldman, Wienke)
JDM has also been associated with an increased risk of malignancy a few years after diagnosis (Wienke, Feldman)

Moral of the Morsel

Be Vigilant! Rare does not mean never. Juvenile dermatomyositis is rare, but also the most common idiopathic inflammatory myopathy in children, and can cause significant morbidity and mortality.
Use your Detective Skills! Look for Grotton’s papules, a heliotrope rash, plus proximal muscle weakness
It is Deeper than the Skin! Look out for the sequelae of JDM such as interstitial lung disease, pneumonia, heart failure, respiratory failure, and malignancy.
Phone a Friend! Consult pediatric rheumatology and discuss starting high dose IV corticosteroids such as methylprednisone.

References:

Barut K, Avar Aydin PO, Adrovic A, Sahin S, Kasapcopur O. Juvenile dermatomyositis: a tertiary center experience. Clin Rheumatol. 2017;36(2):361-366. doi:10.1007/s10067-016-3530-4
Wienke J, Deakin CT, Wedderburn LR, van Wijk F, van Royen-Kerkhof A. Systemic and tissue inflammation in juvenile dermatomyositis: from pathogenesis to the quest for monitoring tools. Front Immunol. 2018;9:2951. doi:10.3389/fimmu.2018.02951
Feldman BM, Rider LG, Reed AM, Pachman LM. Juvenile dermatomyositis and other idiopathic inflammatory myopathies of childhood. Lancet. 2008;371(9631):2201-2212. doi:10.1016/S0140-6736(08)60955-1
Bohan A, Peter JB. Polymyositis and dermatomyositis (Second of two parts). N Engl J Med. 1975;292(8):403-407. doi:10.1056/NEJM197502202920807
Bohan A, Peter JB. Polymyositis and dermatomyositis (First of two parts). N Engl J Med. 1975;292(7):344-347. doi:10.1056/NEJM197502132920706
Mainetti C, Beretta-Piccoli BT, Selmi C. Cutaneous manifestations of dermatomyositis: a comprehensive review. Clinic Rev Allerg Immunol. 2017;53:337-356. doi.org/10.1007/s12016-017-8652-1
Bogdanov I, Kazandjieva J, Darlenski R, Tsankov N. Dermatomyositis: current concepts. Clini Dermatol. 2018;36(4):450-458. doi.org/10.1016/j.clindermatol.2018.04.003
Cancarini P, Nozawa T, Whitney K, Bell-Peter A, Marcuz J, Taddio A, et al. The clinical features of juvenile dermatomyositis: A single-centre inception cohort. Semin Arthritis Rheum. 2022; Available online 25 September 2022. doi:10.1016/j.semarthrit.2022.152104.
Sag E, Demir S, Bilginer Y, et al. Clinical features, muscle biopsy scores, myositis specific antibody profiles and outcome in juvenile dermatomyositis. Semin Arthritis Rheum. 2020;50(1):204-233. doi:10.1016/j.semarthrit.2020.10.007
Kim H. Juvenile dermatomyositis: updates in pathogenesis and biomarkers, current treatment, and emerging targeted therapies. Ped Drugs. 2025;27:57-72. doi.org/10.1007/s40272-024-00658-2
Kishi T, Warren-Hicks W, Bayat N, Targoff IN, et al. Corticosteroid discontinuation, complete clinical response and remission in juvenile dermatomyositis. Rheumatology. 2021;60:2134-2145. doi:10.1093/rheumatology/keaa371
Ravelli A, Trail L, Ferrari C et al. Long-term outcome and prognostic factors of juvenile dermatomyositis: a multinational, multi center study of 490 patients. Arthritis Care & Research. 2010;62(1):63-72. Doi:10.1002/acr.20015
Huber AM, Kim S, Reed AM et al. Childhood arthritis and rheumatology research alliance consensus clinical treatment plans for juvenile dermatomyositis with persistent skin rash. J Rheumatol. 2017;44(1):110-116. Doi:10.3899/jrheum.160688

Author

Taylor Burl

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