How Often are Pediatric Patients with Clinically Amyopathic Dermatomyositis Truly Amyopathic?
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.


CONCLUSIONS
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.
Department of Pediatrics, Section of Pediatric Rheumatology, Nationwide Children's Hospital, Ohio State University, Columbus, Ohio.
Edward J
EJ
Oberle
Department of Dermatology, Medical College of Wisconsin, Milwaukee, Wisconsin.
Michelle L
ML
Bayer
Department of Dermatology, Section of Pediatric Dermatology, Medical College of Wisconsin, Milwaukee, Wisconsin.
Yvonne E
http://orcid.org/0000-0003-2869-2718
YE
Chiu
Department of Pediatrics, Section of Pediatric Rheumatology, Medical College of Wisconsin, Milwaukee, Wisconsin.
Dominic O
http://orcid.org/0000-0001-7760-2411
DO
Co
D000293:Adolescent; D001706:Biopsy; D002648:Child; D002675:Child, Preschool; D003882:Dermatomyositis / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006776:Hospitals, Pediatric; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014922:Wisconsin