Muscle Biopsy: A Requirement for Precision Medicine in Adult-Onset Myopathy

Abstract

Muscle biopsy is a fundamental procedure to assist the final diagnosis of myopathy. With the recent advances in molecular diagnosis, serology tests, and mechanism-based classification in myopathy, the précised diagnosis for myopathy required the applications of multiple tools. This study intends to reappraise the benefit of muscle biopsy in adult-onset myopathy under the setting of an optimized muscle biopsy protocol and comprehensive serology tests. A one-group pretest-posttest study design was used. The pre- and post-biopsy diagnoses and treatments in 69 adult patients were compared. Muscle biopsy yielded 85.5% of definitive diagnoses, including changes in pre-biopsy diagnoses (40.6%) and narrowing down the suspicious myopathies (49.3%). The demographic data and clinical parameters between the group “with change” and “without change” after biopsy were not different. Among those with changes in diagnosis, 39.3% also had a corresponding shift in treatment, which benefits the patients significantly. Regarding the most common adult-onset myopathy, idiopathic inflammatory myopathy (IIM), 41% of patients with pre-biopsy diagnosis as IIM had changes in their IIM subtype diagnosis, and 53% was finally not IIM after muscle biopsy. Although there have been advances in molecular diagnosis recently, muscle biopsy still undoubtedly critically guided the diagnosis and treatment of adult-onset myopathy in the era of precision medicine.

Muscle fibre morphometric analysis (MusMA) correlates with muscle function and cardiovascular risk prognosis

“…53,54 In addition to clinical examination and electrodiagnostic, muscle biopsy and histopathological analysis play a pivotal role by furnishing diagnostic evidence that either confirms a disease's origin or narrows down the possibilities in the differential diagnosis. 54,55 In this scenario, MusMA allows the objective screening of fibre morphometry, which can be combined with clinical parameters to complement the diagnosis while providing prognostic information to predict the risk of muscle failure or loss of function.…”

“…In such a situation, MusMA might be performed within the context of procedures or diseases in which biopsy is already warranted, such as rapidly progressive muscle weakness, immune‐mediated myopathies, muscle degeneration or fibrosis, muscular dystrophies, congenital myopathies, myositis, toxic myopathies, among others 53,54 . In addition to clinical examination and electrodiagnostic, muscle biopsy and histopathological analysis play a pivotal role by furnishing diagnostic evidence that either confirms a disease's origin or narrows down the possibilities in the differential diagnosis 54,55 . In this scenario, MusMA allows the objective screening of fibre morphometry, which can be combined with clinical parameters to complement the diagnosis while providing prognostic information to predict the risk of muscle failure or loss of function.…”

Impaired muscle strength is associated with ultrastructure damage in myositis

“…Another important fact regarding muscle histological examination of IIM patients is the discordance between clinical and histopathological diagnosis that has been previous reported, indicating up to 55% of change in diagnosis after muscle biopsy in IIM patients. Muscle biopsy examination has also a great utility in deep characterization of IIM patients 11 . In our study, the clinical phenotype was not concordant in 30% with muscle biopsy results; this is one of the reasons why the decision of muscle biopsy is debatable nowadays, due to the lack of expertise in its interpretation.…”

Muscle fiber ultrastructure is associated with the immunological profile in idiopathic inflammatory myopathies.

“…Other important fact regarding muscle histological examination of IIM patients is the discordance between clinical and histopathological diagnosis that has been previous reported indicating up to 55% of change in diagnosis after muscle biopsy in IIM patients. Muscle biopsy examination has also a great utility in deep characterization of IIM patients 12 . In our study, the clinical phenotype was not concordant in 30% with muscle biopsy results; this is one of the reasons why the decision of muscle biopsy is discussing nowadays because the lack of expertise in its interpretation.…”