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How Often are Pediatric Patients with Clinically Amyopathic Dermatomyositis Truly Amyopathic?
Edward J Oberle1, Michelle L Bayer2, Yvonne E Chiu3
1Department of Pediatrics, Section of Pediatric Rheumatology, Nationwide Children's Hospital, Ohio State University, Columbus, Ohio.
Insights
Truly amyopathic juvenile dermatomyositis (JDM) is rare, occurring in only 4% of cases. A thorough evaluation including muscle enzymes and MRI is crucial for detecting subclinical muscle inflammation in JDM patients.
Area of Science:
- Pediatric Rheumatology
- Dermatology
- Neurology
Background:
- Juvenile dermatomyositis (JDM) can present with skin manifestations without overt muscle weakness.
- The frequency of clinically amyopathic JDM and subclinical myositis is not well-established.
Purpose of the Study:
- To determine the incidence of clinically amyopathic JDM.
- To assess the frequency of subclinical myositis in JDM patients through comprehensive evaluation.
Main Methods:
- Retrospective review of 46 pediatric patients diagnosed with JDM.
- Evaluation included clinical assessment, five muscle enzymes, MRI, and muscle biopsy.
Main Results:
- 10 patients (21.7%) showed no initial signs of muscle involvement.
- Only 2 patients (4%) were truly amyopathic after full workup (enzymes, MRI, biopsy).
- MRI identified subclinical muscle disease, while muscle biopsy was not informative.
Conclusions:
- Truly amyopathic JDM is uncommon.
- A thorough diagnostic workup, including muscle enzymes and MRI, is essential for uncovering occult myositis in JDM.
Background:
Pediatric patients can present with skin manifestations of dermatomyositis without overt weakness (clinically amyopathic juvenile dermatomyositis [JDM]), but it is unclear how often this happens and how often they have subclinical muscle inflammation.
Objective:
Our goal was to determine the frequency of clinically amyopathic JDM and the frequency with which a thorough evaluation uncovers subclinical myositis at a single institution.
Methods:
A retrospective review was performed of 46 patients diagnosed with JDM at Children's Hospital of Wisconsin.
Results:
Of 46 patients presenting with skin findings consistent with dermatomyositis, 10 patients (21.7%) did not have evidence of muscle involvement on history or exam, and these tended to be the younger patients. Of these 10, only 2 (4% of all the JDM patients) were truly amyopathic upon further evaluation (all five muscle enzymes [aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine kinase and aldolase], magnetic resonance imaging [MRI], muscle biopsy). In our series, muscle biopsy was not helpful in identifying subclinical myositis. In contrast, MRI did uncover subclinical muscle disease.
Conclusion:
These data suggest that truly amyopathic JDM is rare and that a thorough workup that includes all five muscle enzymes and MRI may uncover occult myositis.
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