Low copy numbers of complement C4 and C4A deficiency are risk factors for myositis, its subgroups and autoantibodies
Authors' conclusion
C4A deficiency is relevant in dermatomyositis, HLA-DRB1*03 is important in IBM and both C4A deficiency and HLA-DRB1*03 contribute interactively to risk of polymyositis.
Study context
- Population
- Caucasian patients with idiopathic inflammatory myopathies (IIM) and matched healthy controls
- Participants
- 1,644 vs 3,526
- Comparison
- Patients with IIM vs matched healthy controls
- IIMn = 1,644
- Healthy controlsn = 3,526reference
- Outcome
- Risk of IIM by C4 gene copy number variations (total C4, C4A, C4B)
Methodological detailsmatched healthy controls, real-time PCR or Southern blot analyses
- Matched healthy controls
- Real-time PCR or Southern blot analyses
Main finding
As reported in the abstract
Risk of IIM by C4 gene copy number (GCN)
Odds ratio (CI)P value
Low C4T GCN (C4T=2+3)
2.58(2.28–2.91)
P = 5.0×10-53C4A deficiency (C4A=0+1)
2.82(2.48–3.21)
P = 7.0×10-57Observational data: associations, not effects.
Further findings
HLA-DR3 as risk factor among patients with C4A deficiency
| OR (CI) | ||
|---|---|---|
| HLA-DR3 in IBM98.2% had HLA-DR3 | 11.02 (1.44–84.4) | |
| 0.050.21520Odds ratio (log scale) |
- HLA-DR3 insignificant as a risk factor in IIM except for inclusion body myositis (IBM)
C4 plasma concentrations by IIM-related autoantibodies
- Patients with anti-Jo-1 or anti-PM/Scl had significantly lower C4 plasma concentrations than those without
Original publication
Low copy numbers of complement C4 and C4A deficiency are risk factors for myositis, its subgroups and autoantibodies. Ann Rheum Dis. Published 28 September 2022. doi:10.
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