Clinical History
A 12-year-old girl presents with a chief complaint of progressive fatigue, weakness, and dyspnea on exertion, which has been ongoing for the past two months. She also reports a rash on her face, as well as on the extensor surfaces of her hands and knees. Additionally, she has experienced fever, decreased appetite, joint pain, and a 15-pound weight loss.
Her family history is notable for asthma and rheumatoid arthritis. Laboratory results show that she is positive for anti-MDA5 serology.
What is the likely diagnosis?
A. Amyopathic dermatomyositis
B. Psoriatic (overlap) myositis
C. Juvenile myositis
D. Lupus myositis
Answer: Amyopathic Juvenile dermatomyositis
Amyopathic dermatomyositis may show neither inflammation nor perimysial pathology; however MHC, class I (aka HLA-ABC) is more sensitive to detect pathology
MxA positivity of muscle fibers is a relatively sensitive and specific marker for dermatomyositis seen in both adults and children
MDA5 antibodies associated with mild/absent pathology on H&E (amyopathic), arthritis and/or skin ulceration
90% of juvenile myositis is associated with skin disease
Reference(s) / additional reading:
- Nix JS, Moore SA. J Neuropathol Exp Neurol. 2020;79:719-733.
- Tanboon J, Uruha A, Stenzel W, Nishino I. Curr Opin Neurol.2020;33:590-603.
- Allenbach Y, et al. Neuropathol Appl Neurobiol. 2017;43:62-81.
- Halilu F, Christopher-Stine L. Rheumatol Immunol Res. 2022;3:1-10.
Quick note: This post is to be used for informational purposes only and does not constitute medical or health advice. Each person should consult their own doctor with respect to matters referenced. Arkana Laboratories assumes no liability for actions taken in reliance upon the information contained herein.
