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|Year : 2021 | Volume
| Issue : 3 | Page : 642
Sporadic Inclusion Body Myositis (Sibm): Challenges in Diagnosis and Treatment
Department of Neurology, AIIMS, Delhi, India
|Date of Submission||20-Mar-2021|
|Date of Decision||28-Apr-2021|
|Date of Acceptance||04-May-2021|
|Date of Web Publication||24-Jun-2021|
Dr. Deepti Vibha
Department of Neurology, AIIMS, Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Vibha D. Sporadic Inclusion Body Myositis (Sibm): Challenges in Diagnosis and Treatment. Neurol India 2021;69:642
The case series by Murthy et al. on sIBM collected over five years, is, therefore, an important step towards defining the clinic-pathological characteristics. Sporadic Inclusion Body Myositis (sIBM) is characterized by the slow and progressive asymmetric weakness and atrophy of proximal and distal muscles, preferentially involving finger flexor and quadriceps muscle groups. A combination of unique clinical, pathological and lack of treatment responsiveness makes it an enigmatic disease. First described in 1978 as case series of six cases, it has undergone several revisions in its classification and diagnostic criteria since then. The most recent classification is the European Neuromuscular Center (ENMC) IBM research diagnostic criteria 2011, which divides it into clinic-pathological IBM, clinical IBM and probable IBM. Duration of more than 12 months, age of more than 45 years, weakness of knee extensors and finger flexors in combination with a creatine kinase of >15 times the upper limit of normal constitutes the clinical criteria. Pathologically, the presence of endomysial inflammatory infiltrates, up-regulation of MHC class I T-cells, rimmed vacuoles, protein accumulation (amyloid or other protein accumulation) or 15–18 nm filaments characterize sIBM. Hence, the presence of a clinical neurology and pathology team with expertise as well as infrastructure is required to diagnose and manage this challenging diagnosis.
To add to the confusion, the term, hereditary inclusion body myopathies (hIBMs) (disorders due to mutations in GNE, VCP or MYH2) are also sometimes abbreviated as IBM, despite not sharing any clinical or pathological features. They neither resemble in a pattern of muscle weakness and do not have muscle immune cell infiltration on histology.
The prevalence studies of sIBM are very few and in limited parts of the world with an estimate of 45.6/1,000,000 (95% CI: 35.9–55.2). The prevalence is not known in the Indian population. The reasons are challenges in the ascertainment of the diagnosis in resource poor settings as well as the evolving diagnostic criteria. The treatments which are FDA-approved so far are intravenous immunoglobulin, with and without prednisone, methotrexate, interferon beta and oxandrolone, bimagrumab and arimoclomol. All these treatments have shown minor or no clinically meaningful benefit in clinical trials.
Although most of the cases were classified as probable, this was mainly due to the inability to demonstrate amyloid in the vacuoles. All patients were unresponsive to steroids, and a systematic follow up of disability progression and outcome over time may have added to the knowledge of the behaviour of the rare disease. The study highlights the advantages of a well-defined classification system for this rare inflammatory myositis. It provides a repository of clinic-pathological information, which is lacking from this part of the world.
| » References|| |
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