From the Guidelines
Inclusion body myositis (IBM) is not primarily caused by genetic factors, but rather is considered a sporadic disease with possible genetic predisposition and environmental triggers. The diagnosis of IBM is based on specific criteria, including finger flexor weakness and response to treatment, or muscle biopsy showing rimmed vacuoles 1. While there is a rare hereditary form of IBM with a genetic basis, most cases are sporadic and occur without a clear family history. Certain genetic variations, such as those in the HLA region, may increase susceptibility to IBM, but the exact role of genetics in the disease is still not fully understood 1.
Key characteristics of IBM include:
- Progressive muscle weakness and wasting, particularly affecting the quadriceps, finger flexors, and swallowing muscles
- Poor response to conventional immunosuppressive treatments
- Management focusing on physical therapy, assistive devices, and supportive care rather than medication
The 2017 European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups provide a framework for diagnosing and subclassifying IBM, but do not support a primary genetic cause 1. Overall, while genetic factors may contribute to susceptibility, IBM is not primarily considered a genetic disease.
From the Research
Genetic Factors in Inclusion Body Myositis (IBM)
- Genetic factors are known to contribute to the susceptibility of sporadic inclusion body myositis (sIBM) 2.
- The major histocompatibility complex (MHC) has been associated with sIBM, with different combinations of alleles linked to the disease in various ethnic groups 3.
- Specific HLA alleles and amino acids have been identified as risk factors for IBM, including HLA-DRB103:01, DRB101:01, and DRB1*13:01 4.
- Amino acid positions 26 and 11 of the HLA-DRB1 molecule have also been associated with IBM 4.
- Other genetic regions, such as the chromosome 3 p21.31 region, have been suggested as potential risk loci for IBM 4.
- Familial cases of inclusion-body myositis (fIBM) provide additional evidence for genetic susceptibility, although the genes responsible for these conditions are not thought to be involved in sIBM 3.
- Advanced genetic technology, such as whole-exome sequencing, may help to unravel important genetic risk factors for sIBM 5.
Limitations of Current Knowledge
- Despite some evidence for genetic susceptibility, the current understanding of the genetic contributions to sIBM is limited 6, 5.
- The causes of sIBM are still unknown and are considered complex, involving multiple factors such as environmental triggers, aging, and genetic susceptibility 5.
- Further research is needed to fully understand the genetic factors involved in IBM and to develop effective treatments for the disease 2, 5.