2014;2:154. 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; considerable 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 PTC-209 mass biopsy, myositis antibodies INTRODUCTION Autoimmune myositis, also called as idiopathic inflammatory myopathies (IIM), are a heterogeneous group of diseases involving muscular as well as extramuscular manifestations including cutaneous, lung, and joints among others. The major subgroups of IIM include dermatomyositis (DM), inclusion body myositis (IBM), immune-mediated necrotizing myopathy (IMNM), and anti-synthetase syndrome (ASS).[1,2] Others include overlap myositis and nonspecific myositis. Polymyositis (PM) is usually of late not considered as a distinct entity.[2] Numerous autoantibodies associated with IIMs have been discovered, beginning with anti-Mi2, back in 1976.[3] There has been a constant stride to classify this polyphenotypic group of diseases into clinically meaningful, pathologically informative, and diagnostically reproducible entities. The classification schemas and diagnostic criteria are constantly being revised. However, some of the classification schemas are widely accepted Rabbit Polyclonal to RNF111 among others. The classification of autoimmune myositis has evolved over the decades from clinical to clinico-pathologic and to the recent clinico-sero-pathologic. This is reflected in various diagnostic schema beginning with Bohan and Peter in 1975, Dalakas in 1991, and the various revisions of European Neuromuscular Centre (ENMC) classification criteria.[4,5,6,7,8,9] The inclusion of serologic features into diagnostic criteria provides a noninvasive yet robust technique for diagnosis. Several myositis-specific (MSA) and myositis-associated (MAA) antibodies have been detected in the sera of myositis patients. The various antibodies have been shown to be associated with specific phenotypes, organs involved, and severity.[10] Over time, the biotechnological advancements have paved way for various platforms for the detection of autoantibodies.[11] Of these, the immunoblot technique is relatively simple to perform, reproducible, and widely available with promising results. Ready-to-use PTC-209 panel of antigens is now available in the form of strip tests to this end, which is being incorporated into routine practice for diagnosis of DM, IMNM, and ASS cases. However, about one-third of myositis cases are sero-negative.[12] The antibodies can also fluctuate during the disease course and in response to treatment.[13,14] Muscle biopsy is required in such cases as well as in cases with atypical presentation to establish a diagnosis, in addition to diagnosis of IBM. In this study, we compare the muscle biopsy features with the respective autoantibodies. This is a pilot experience to explore the morphologic spectrum of IIM with respect to each antibody. MATERIALS AND METHODS This was a retrospective study done in the department of Pathology, Nizams Institute of Medical Sciences (NIMS) after obtaining approval from the institutional ethics committee (64th ESGS No. 1406/2022). The study group included all PTC-209 the patients with clinical diagnosis of IIM in whom muscle biopsy was performed and the myositis profile was positive. All such cases from January 2019 to December 2022 were included in the study. The muscle biopsy interpretation as well as myositis profile for all the cases was performed at our hospital in department of pathology. The clinical and demographic features, Creatine phosphokinase and Electroneuromyography (CPK and ENMG) results were obtained from patient request forms. Muscle biopsy The biopsies were snap frozen.