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Condition report · Musculoskeletal

Rheumatoid Arthritis

Whole genome sequencing identifies HLA and immune pathway variants that shape rheumatoid arthritis risk and treatment response, providing a more complete picture for you and your physician.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

A chronic, systemic autoimmune disorder characterized by inflammation in the synovial membranes and articular surfaces. It manifests primarily as a symmetric, erosive polyarthritis that spares the axial skeleton and is typically associated with the presence in the serum of rheumatoid factor.

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by symmetrical polyarticular inflammation leading to progressive joint destruction and loss of function. Prevalence is approximately 0.5-1% of the global population, affecting women approximately 2.5 times more commonly than men, with typical onset between ages 40 and 60 (though any age can be affected). Heritability is estimated at approximately 60%, indicating strong genetic contribution to disease development. More than 100 GWAS loci have been identified as contributing to RA susceptibility; the strongest genetic risk factors are in the HLA region, particularly specific HLA-DRB1 alleles sharing a common amino acid sequence in the peptide-binding groove called the 'shared epitope' (SE).

HLA-DRB1 and PTPN22 together account for approximately 40% of the total genetic risk in RA. HLA-DRB1 encodes a Major Histocompatibility Complex (MHC) class II molecule; specific HLA-DRB1 alleles (DRB1*04:01, DRB1*04:04, DRB1*01:01) share amino acid sequences (positions 71, 74) that define the 'shared epitope.' This shared epitope preferentially binds and presents citrullinated peptides to CD4+ T cells, driving autoreactive T cell activation and producing anti-citrullinated protein antibody (anti-CCP) responses characteristic of RA. PTPN22 encodes protein tyrosine phosphatase N22, involved in T cell receptor signaling; loss-of-function variants (Arg620Trp) paradoxically increase autoreactive T cell activation.

RA is not a simple Mendelian disease but rather a complex multigenic condition where multiple genetic risk factors combine with environmental triggers (smoking, infections, dietary factors) and immunological events to produce disease. HLA-DRB1 shared epitope typing has prognostic value: patients carrying shared epitope alleles have higher rates of anti-CCP positivity, more severe radiographic changes, worse clinical outcomes, and higher response rates to certain DMARDs. Understanding the genetic basis of RA has led to targeted therapies: IL-23 pathway inhibition (ustekinumab, risankizumab, guselkumab) was developed based on GWAS identification of IL23R as an RA susceptibility locus, now providing new treatment options for patients who do not respond to conventional therapies.

The condition we analyse

A chronic, systemic autoimmune disorder characterized by inflammation in the synovial membranes and articular surfaces. It manifests primarily as a symmetric, erosive polyarthritis that spares the axial skeleton and is typically associated with the presence in the serum of rheumatoid factor.

What a diagnosis changes

DMARDs, biologic immunomodulators, NSAIDs, physical therapy, genetic counseling

Also known as

RA

Includes 10 related subtypes ↓
  • ankylosing spondylitis
  • chronic childhood arthritis
  • Felty syndrome
  • juvenile ankylosing spondylitis
  • juvenile spondyloarthropathy
  • polyarticular juvenile rheumatoid arthritis
  • psoriasis-related juvenile idiopathic arthritis
  • psoriatic arthritis
  • rheumatoid arthritis-associated interstitial lung disease
  • rheumatoid vasculitis
MONDO:0008383OMIM 180300Orphanet 284130MedGen 2078

Why whole genome sequencing

Genetic testing is not standard for RA diagnosis. WGS enables comprehensive risk profiling as clinical implementation emerges.

RA involves >100 genetic loci, each with small individual effect

Genetic contribution to RA involves more than 100 loci, each with small individual effect sizes; current single-gene or limited gene panels cannot capture all contributors. HLA-DRB1 typing is sometimes performed for prognosis assessment but is not routine. Genetic testing does not replace the clinical diagnosis and serological workup (rheumatoid factor, anti-CCP antibodies). However, whole genome sequencing provides the comprehensive GWAS variant data necessary for future polygenic risk score calculation, enabling individualized genetic risk assessment that may eventually guide therapy intensity and inform family screening.

Genetic understanding has transformed RA drug development

The landmark discovery that IL23R variants protect against RA led directly to therapeutic development: IL-23 pathway inhibitors (ustekinumab, risankizumab, guselkumab) are now approved for RA, producing dramatic responses in subgroups of patients. Similarly, STAT4 identification as a susceptibility locus has guided development of STAT4-targeting therapies. Understanding the genetic basis of RA has principally driven drug development and may eventually enable personalized medicine approaches: selecting specific biologic therapies based on individual genetic profiles to optimize response rates and minimize side effects.

Other musculoskeletal conditions

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