daily folic acid supplementation . He was eventually discharged home with continued improvement in his motor strength and scheduled follow-up with pediatric rheumatology and physical therapy .
DISCUSSION
JDM has an incidence of approximately three out of one million children in the United States per year but accounts for 85 % of the idiopathic inflammatory myopathies of childhood . Though 25 % of children are under the age of 4 years when symptoms first manifest , the average age of presentation is 7 years old . 1 Our patient was 3 years old at the time of diagnosis , adding to the limited number of case reports on patients presenting at this early age . 2-4
The manifestation of classic clinical symptoms can aid in recognition of this rare disease . According to one study of the prevalence of various clinical features of JDM in a facility in Turkey , a heliotrope rash and Gottron papules were found in 100 % and 96 % of the patients , respectively , with muscle weakness present in 90 %; other erythematous rashes were present in 88 %. 5 Similarly , in the United States , 100 % of the patients present with both Gottron papules / heliotrope rash and muscle weakness . 1
The differential diagnosis of patients who present with similar findings to our patient can be broadly categorized into myositis , including infectious ( bacterial or viral ) versus idiopathic ( JDM or polymyositis ); primary or secondary ( endocrine , nutritional ) myopathies ; neuromuscular diseases such as Guillain-Barre ; and connective tissue diseases with associated myositis , including SLE . 1 Juvenile idiopathic arthritis was also considered but less likely in this case given a normal joint examination .
The diagnostic criteria for JDM established in 1975 by Bohan and Peter includes :
1 . Classic skin rashes ( Gottron papules , “ shawl sign ”)
2 . Symmetrical proximal muscle weakness
3 . Elevation of sarcoplasmic enzymes ( AST , ALT , LDH , CK , aldolase )
4 . Myopathic electromyographic ( EMG ) abnormalities
5 . Characteristic muscle pathology
Definitive diagnosis requires the presence of a rash as well as three of the remaining criteria , and a probable diagnosis requires the presence of a rash and only two additional criteria . 1 However , secondary to their invasive nature and limited accessibility , EMG and muscle biopsies are rarely performed today , especially in children , leading to the development of classification criteria for adult and juvenile idiopathic inflammatory myopathies by the European League Against Rheumatism / American College of Rheumatology in 2017 . 6 In this case , characteristics including age of onset , muscle weakness , skin manifestations , other clinical manifestations ( dysphagia , esophageal dysmotility ), and laboratory measurements ( anti-Jo-1 , CK , LDH , aspartate aminotransferase , alanine aminotransferase ) with or without muscle biopsy are assigned points , and the total aggregate score corresponds with the probability of idiopathic myopathy . 6 If the probability is greater than or equal to 55 %, the myopathy can be further classified , based on age of onset , into adult myopathies versus juvenile myopathies . Juvenile myopathies are further subdivided into JDM if a heliotrope rash , Gottron ’ s papules , or Gottron ’ s signs are present , and juvenile myositis if these findings are absent . 6 In this case , the patient had symmetric proximal muscle weakness , classical skin rashes , and elevation of CK , aldolase , and LDH , with a total score of 8.9 consistent with a greater than 90 % probability of having idiopathic inflammatory myopathy . 6 The classical skin rashes place him in the JDM category . 6 Patwardhan et al . utilized MRI in their modified criteria to diagnose JDM . 7
It must be noted that younger children may not present in the classic manner expected in JDM . Patwardhan et al . described patients under three years of age presenting with non-classical signs , including lack of cutaneous manifestations ( Gottron ’ s papules and heliotrope rash ). 7 They also described patients in this age group as having less abnormalities in muscle enzymes as well as not requiring hospital admission or treatment with pulse dose steroids . 7 Our patient described in this case report had classical cutaneous symptoms , abnormal muscle enzymes , and required hospitalization and treatment with high dose intravenous steroids due to the severity of his symptoms .
In addition to the more common proximal muscle weakness of the hip and shoulder girdles leading to the classic difficulties with brushing hair or climbing stairs , pharyngeal , hypopharyngeal , palatal , and respiratory muscle weakness can be present , manifesting as dysphonia , dysphagia , and respiratory insufficiency . Oligo- or poly-articular non-erosive arthritis and calcinosis can cause joint contractures , disability , nerve entrapment , and disfigurement , which can present as the disease progresses . Though rare , cardiac involvement can also be seen and should be monitored for as well . 1
Treatment is aimed at inducing and maintaining remission to allow children to continue to participate in their daily activities . Steroids are the first-line treatment to stop the disease process ; with their use , mortality has decreased from 33 % to < 2 %. 8 Though there can be considerable variation in clinical practice in the treatment of JDM , consensus conferences in 2007 and 2010 developed three standardized protocols for the initial two months of treatment of moderately severe disease followed by a steroid tapering plan . 8 , 9
For all the protocols , dietary modifications with dietary consultations , sunscreen counseling , and folic acid supplementation are required . Calcium and vitamin D supplementation and referral to physical and / or occupational therapy are also recommended . 8
Additional therapies such as IV methylprednisolone , IVIG , cyclosporine , mycophenolate mofetil , azathioprine , or biologic agents may be required without patient improvement . 9 JAK kinase inhib-
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