Comparison of Muscle Biopsy Features with Myositis Autoantibodies in Inflammatory Myopathies: A Pilot Experience

Archana Gudipati; Shaikh Rifat; Megha Uppin; Afshan Jabeen; Niharika L Mathukumalli; Sireesha Yareeda; Sunitha Kayidhi; Anjan Pyal; Megha Dhamne; Y Muralidhar Reddy

doi:10.4103/aian.aian_142_23

Comparison of Muscle Biopsy Features with Myositis Autoantibodies in Inflammatory Myopathies: A Pilot Experience

Ann Indian Acad Neurol. 2023 Jul-Aug;26(4):408-418. doi: 10.4103/aian.aian_142_23. Epub 2023 Aug 25.

Authors

Affiliations

¹ Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
² Department of Neurology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana, India.
³ Department of Consultant Rheumatologist, Continental Hospital, Hyderabad, Telangana, India.
⁴ Department of Consultant Neurologist, Citi Neuro Centre, Hyderabad, Telangana, India.
⁵ Department of Consultant, PD Hinduja Hospital, Mumbai, Maharashtra, India.
⁶ Department of Consultant Neurologist, Care Hospital, Banjara Hills, Hyderabad, Telangana, India.

Abstract

Background: Idiopathic inflammatory myopathies (IIM), also called autoimmune myositis, are heterogeneous. These include dermatomyositis (DM), inclusion body myositis, immune mediated necrotizing myopathy (IMNM), anti-synthetase syndrome (ASS), and overlap polymyositis. Classification of IIM has evolved from clinical to clinico-pathologic to the recent clinico-sero-pathologic with the discovery of myositis-specific antibodies (MSA) and myositis-associated antibodies. The various antibodies have shown association with specific phenotypes.

Objective: To analyze muscle biopsy features with respect to each MSA and MAA to understand the frequency of findings in each entity.

Materials and methods: Biopsy-proven cases of IIM where myositis profile was available were included in the study after obtaining Institutional Ethics Committee (IEC) approval. In addition to the stains and enzyme histochemistry, immunohistochemistry with MHC class I and II and MxA was performed. Features like perifascicular atrophy, perifascicular necrosis, scattered necrosis, inflammation, etc. were analyzed. Myositis profile was performed by line-blot technique using a 16-antigen panel. Cases were divided into different autoantibody subgroups. Various clinical, demographic, and muscle biopsy features were studied with respect to each MSA and MAA.

Results: There were a total of 64 cases. Mi2 (N = 18) was the most common autoantibody. Some of the salient observations included PFA with perivascular inflammation in Mi2; pediatric cases and microinfarcts in NXP2; no PFA or inflammation in MDA5; perifascicular necrosis in JO1; extensive necrosis with sparse inflammation in SRP; more inflammation in overlap myositis; MxA positivity in DM; and absent in ASS.

Conclusion: This is a pilot study documenting differences in biopsy phenotype with each MSA and MAA which is comparable to the literature. These findings can be used to characterize IIM in seronegative biopsies.

Keywords: Inflammatory myopathy; muscle biopsy; myositis antibodies.