Anan, R., Akiyama, M., Kaneko, Y., Kikuchi, J., Suzuki, K., Matsubara, S., & Takeuchi, T. (2017). Polymyositis with elevated serum IgG4 levels and abundant IgG4+ plasma cell infiltration: A case report and literature review. Medicine, 96(48), e8710. https://doi.org/10.1097/MD.0000000000008710

Diagnosis - Polymyositis (PM) - Diseases | Muscular Dystrophy Association. (2024, May 15). Muscular Dystrophy Association. https://www.mda.org/disease/polymyositis/diagnosis#:~:text=People%20with%20polymyositis%20(PM)%20may,exclusion%20of%20other%20IIM%20subgroups.

Findlay, A. R., Goyal, N. A., & Mozaffar, T. (2015). An overview of polymyositis and dermatomyositis. Muscle & nerve, 51(5), 638-656.

JoVE (Journal of Visualized Experiments). (2022, July 6). Modified Bergstrom Technique for Human Skeletal Muscle Biopsy | Protocol Preview. YouTube. https://www.youtube.com/watch?v=Azv2s6JVdqM

Milisenda, J., Selva-O’Callaghan, A., & Grau, J. (2014, February 1). The diagnosis and classification of polymyositis. Journal of Autoimmunity. https://doi.org/10.1016/j.jaut.2014.01.025

Muscular Dystrophy Association. (n.d.). Muscular Dystrophy Association. https://www.mda.org

Sarwar, A., Dydyk, A. M., & Jatwani, S. (2020). Polymyositis. PubMed; StatPearls

Seetharaman, M. (n.d.). Polymyositis Workup: Approach Considerations, Imaging Studies,  Electromyography. https://emedicine.medscape.com/article/335925-workup?form=fpf

(2024). Amboss.comhttps://next.amboss.com/us/search?q=polymyositis&v=overview

YouTube. (2021, March 12). Polymyositis. YouTube. https://www.youtube.com/watch?v=yw87XQWXTPo

Elevated serum creatinine kinase (384 IU/L, normal range: 50–170 U/L):

• Creatine kinase is an enzyme found in muscle cells. When muscle damage occurs, creatine kinase leaks into the bloodstream, causing elevated levels. The degree of elevation can provide clues about the severity of muscle damage. In this case, a significant increase suggests substantial muscle involvement.

Elevated aldolase (6.2 IU/L, normal range: 2.7–5.9 IU/L):

• Similar to creatine kinase, aldolase is another enzyme found in muscle cells. Its elevation further supports muscle damage.

Elevated lactate dehydrogenase (314 U/L, normal range: 120–220 U/L):

• Lactate dehydrogenase is an enzyme present in various tissues, including muscle. While not specific to muscle damage, its elevation alongside creatine kinase and aldolase strengthens the suspicion of myopathy

Histological examination of left quadriceps: mononuclear inflammatory cells that surrounded and invaded muscle fibers (were positive for CD8 and MHC class I antigen was extensively expressed on the surface of almost all muscle fibers).

Scattered necrotic and regenerating muscle fibers as well as variations in muscle fiber size were characteristic of inflammatory myopathy (Image A and B).

Infiltration of inflammatory cells at perivascular sites and perifascicular atrophy were not observed.

CD138, IgG, and IgG4 immunostaining revealed that over 40% of infiltrated IgG positive plasma cells were IgG4+ cells (Image E, F, G)

Important findings for IgG4-RD of storiform fibrosis and obliterative phlebitis were not found (ImageH).

Blood counts, serum levels of electrolyte, creatinine, IgE, and blood glucose, within normal range.

Antinuclear antibody was positive with a titer of 1:1240 (homogeneous and speckled patterns).

Anti Aminoacyl-tRNA synthetase, anti-RNP, anti-dsDNA antibody, and anti-Sm antibodies were all negative.