LO: Describe the efficacy, safety, suitability and mechanism of action of DMARDs and Biologics in the treatment of Rheumatoid arthritis

HLA-B27

• Proteins on almost every cell surface in the human body
• On chromosome 6
• More than 200 HLA-B27 subtypes
• Conditions may occur simultaneously or sequentially

Prevalence

• 6-8% of UK population
• Risk of developing related condition increases to 10-15% if HLA-B27 positive

Psoriatic arthritis

• Incidence = 0.5% of general population
• Female to male ratio $\approx$ 1:1
• Peak incidence in 25-50 years
• 1 in 4-5 people with skin psoriasis
• Nail lesions can predict arthritis (90% with, 40% without)

Patterns

• Asymmetrical oligoarthritis (<5 joints) - 30-40%
• Symmetrical polyarthritis (RA mimic) - 30%
• Distal arthritis (DIPj predominant) - 10-15%
• Arthritis mutilans - <10%
• Spondyloarthropathy - 10-20%

Psoriatic arthritis response criteria (PsARC)

• Patient global assessment (score between 1-5)
• Physician global assessment (score between 1-5)
• Joint pain/tenderness score (68 joints)
• Joint swelling score (66 joints)

Investigations

• Bloods
  • CRP
  • 50-60% with psoriatic arthritis have normal CRP levels
  • Elevated CRP tends to be more common in patients with specific features

Imaging

• Pencil in cup deformity

Treatments

• DMARDs - methotrexate (MTX), sulfasalazine (SSZ), Leflunomide (LEF)
• Apremilast - oral small molecule phosphodiesterase 4 (PDE4) inhibitor
• Biologics

Axial spondyloarthritis (axSpA)

• Incidence = 0.3-1.2% general population
• Female to male ratio $\approx$ 1:1
• Peak incidence in 20-40

Inflammatory back pain (IBP)

• Insidious onset
• Duration: >3 months
• Relieved by exercise
• Not relieved by rest
• Morning stiffness >30 minutes
• Nocturnal pain
• Alternating buttock pain
• Good response to anti-inflammatory drugs
• Not all IBP is axSpA
• IBP present in 75% of axSpA going up to 88% during the course of the disease

Problem

• 5% of GPs were able to identify all IBP features
• Low agreement between referring clinicians and rheumatologists on the presence of IBP has been repeatedly observed

Investigations

• HLA-B27
  • 60-90% of patients with axSpA are HLA-B27 positive
• Imaging
  • MRI - whole spine, ankylosing spondylitis (AS) protocol
  • X-ray

Extra-articular manifestations

• Ocular - anterior uveitis
• Cardiac
• Renal - effects of NSAID use, amyloidosis
• Pulmonary - ILA (apical)
• Osteoporosis - from poor bone mineral density (BMD) and spinal restriction

Treatment

• NSAIDs - evidence to show they slow progression
• DMARDs - no role
• Biologics - anti-TNF, IL17i, JAKi
• Exercise
• Surgery

Reactive arthritis

• Arthritis is sterile, preceding infectious trigger
• Typical onset 1-6 weeks after the triggering infection
• Chlamydia trachomatis
• GI infection
• Triad - arthritis, conjunctivitis and urethritis
• Incidence = 0.6-27 cases per 100,000
• Female to male ratio $\approx$ 1:9
• Most cases occur in young adults, 18-40
• HLA-B27 present in 50-96% of patients

Presentation

• Large joint oligoarthritis
• Clinical triad (Reiter's syndrome - Julius Reiter, Nazi war criminal)

Treatment

• NSAIDs, corticosteroids, DMARDs/Biologics for refractory cases

Prognosis

• Recover within 6 to 12 months
• Approximately 15 to 30% progress to chronic spondyloarthropathy
• Recurrence more common with chlamydia infection than enteric infection trigger or HLA-B27 positive

Enteropathic arthritis

• Ulcerative colitis (UC) and Crohn's disease
• SpA 30x more compared with normal population
• Independent of bowel symptoms/severity
• HLA-B27: 50-70% with ankylosing spondylitis, <50% with only sacro-ileitis
• Presentation
  • Polyarthritis usually asymmetrical large joint
• Treatment
  • MDT approach with gastroenterology
  • Pharamcological (DMARDs/Biologics)
  • Surgical - UC proctocoloectomy