Diagnosing inclusion body myositis (IBM) accurately is crucial for effective management and care. Because IBM shares symptoms with other neuromuscular conditions, a combination of diagnostic tests is typically required to reach a definitive Inclusion Body Myositis Diagnosis. Individuals suspected of having IBM may present with a range of indicators that necessitate thorough evaluation.
| Test | Characteristic findings |
|---|---|
| Clinical Symptoms | Frequent falls, reduced hand and finger dexterity, and progressive muscle weakness are common indicators of IBM. |
| Clinical Examination | Physical assessments often reveal asymmetric muscle weakness, particularly affecting distal muscles, hip flexors, and knee extensors. |
| Blood Tests | Elevated levels of creatine kinase (CK) and other muscle enzymes in blood samples can suggest muscle damage. Blood tests may also identify specific antibodies related to myositis or other autoimmune disorders. |
| Myositis Autoantibody Testing | The presence of myositis-specific autoantibodies, such as anti-NT5C1A, can strongly support an IBM diagnosis. |
| Electrophysiological Studies | Electromyography (EMG) can detect a distinctive pattern of electrical activity within affected muscles. Nerve conduction velocity (NCV) tests assess nerve function and help differentiate IBM from neuropathies. |
| Magnetic Resonance Imaging (MRI) | Muscle MRI may reveal signs of muscle atrophy (thinning) and edema (swelling) in affected areas, aiding in the diagnostic process. |
| Muscle Biopsy | A muscle biopsy remains the gold standard for confirming IBM. Microscopic examination can reveal hallmark features of IBM. |
Muscle biopsy is considered the definitive diagnostic test for inclusion body myositis diagnosis. A muscle biopsy from a patient with IBM exhibits unique pathological features, most notably inclusion bodies, which give the disease its name. These inclusion bodies are abnormal accumulations of cellular proteins within muscle fibers. Additionally, the biopsy often shows rimmed vacuoles, which are empty spaces within muscle cells. Inflammatory cells, such as cytotoxic T cells and macrophages, are also typically observed infiltrating the muscle tissue. While inflammation is present, some researchers propose that it might be a secondary response to the underlying muscle damage that leads to the formation of inclusion bodies.
Ultimately, a comprehensive approach utilizing clinical evaluation, blood tests, electrophysiological studies, imaging, and muscle biopsy is essential for accurate inclusion body myositis diagnosis and to differentiate it from other muscle diseases.
References
- Inflammatory Muscle Diseases. N. Engl. J. Med. (2015). doi:10.1056/nejmc1506827
- Lotz, B. P., Engel, A. G., Nishino, H., Stevens, J. C. & Litchy, W. J. Inclusion body myositis: Observations IN 40 patients. Brain (1989). doi:10.1093/brain/112.3.727
- Greenberg SA. Inclusion body myositis: clinical features and pathogenesis. Nat Rev Rheumatol. 2019;15(5):257-272. doi:10.1038/s41584-019-0186-x
- Naddaf E. Inclusion body myositis: Update on the diagnostic and therapeutic landscape. Front Neurol. 2022;13:2236. doi:10.3389/FNEUR.2022.1020113/BIBTEX
Last update: Feb 2023 Reviewed by Julie Paik, MD, MHS; Johns Hopkins University
