LO: Discuss the presentation, initial investigation, key differential diagnosis and initial management of polyarticular joint pain

• Polyarthritis - many joint inflammation
• Polyarthralgia - many joint pain
• More than 4 joints involved
• Oligo (2-4)
• Mono (1)

History and examination

• Most important aspect of trying to formulate investigations and management plans
• Inflammatory vs non-inflammatory
• Pain due to arthritis or arthralgia
• Distribution of joint involvement
• Extra-articular features
• Pattern of joint involvement: Migratory, Additive, Intermittent

Dermatological manifestations

• Erythema chronicum migrans - Lyme
• Erythema nodosum - sarcoid
• Psoriatic plaques - psoriatic arthritis
• Keratoderma blenorrhagicum - reactive arthritis

Causes of acute polyarthritis

Disseminated gonococcal infection

• Young, healthy adults
• 1-3% with gonorrhoea
• Migratory polyarthraldia/arthritis
• Skin rash - common but subtle
• 25% have genitourinary symptoms
• Less than 25% with positive joint cultures
• Positive blood cultures rare
• Treatment - Antibiotics (ceftriaxone)

Investigations

• Bloods
  • Full blood count
  • Renal function
  • Liver function tests
  • Inflammatory markers - ESR/CRP
  • Immunology: rheumatoid factor, anti-nuclear antibody
  • Uric acid, thyroid-stimulating hormone, iron studies, HLA-B27
• Radiology
  • Plain x-rays
  • Ultrasound and MRI
• Synovial fluid
  • Consider if suspicion of bacterial joint infection of crystal arthritis

Chronic inflammatory causes

• Rheumatoid arthritis
• Spondyloarthropathies: axial spondyloarthropathy, psoriatic arthritis
• Seronegative/B27 related: above and enteropathic arthritis, reactive arthritis
• Crystal arthritis: gout, CPPD
• Connective tissue disease: SLE, scleroderma, myositis
• Vasculitis
• Sarcoid, adult onset Stills disease

Joint distribution

LO: Discuss the basic epidemiology, presentation, investigation, management and prognosis of Lyme disease

Lyme disease

• Tick borne - peak onset in spring and summer
• Borrelia burgdorferi
• Erythema chronicum migrans - diagnostic skin lesion occurring at site of the bite: 1-4 weeks after bite
• Disseminated infection can affect the heart, nervous system and joints
• Early localised - ECM, flue like sx
• Early disseminated - facial nerve palsies, lymphocytic meningitis, conduction abnormalities, carditis
• Late disease - neurological, arthritis
• Treatment - doxycycline if early, IV antibiotics if late

Rheumatic fever

• Causes migratory polyarthritis, usually in children
• Systemic inflammatory syndrome occurring in the setting of those with group A streptococcus
• Common cause of acquired valvular heart disease in the world
• Jones criteria - diagnosis
  • 1 major = 2 minor, $\sum$ =2 major
  • Major: carditis, arthritis, chorea, erythema marginatum, subcutaneous
  • Minor: arthralgia, fever, elevated CRP/ESR, prolonged PR interval
• Arthritis - typically migrating, tends to affect large joints of the lower limb
• Treatment - antibiotics

Common viral infections

• Majority are self limiting (resolve on their own) and do not cause permanent joint damage
• Almost any virus can cause arthralgia or a self limiting arthritis
• History including exposures and travel are important to diagnose
• Can cause autoantibodies such as rheumatoid factor and anti-nuclear antibodies
• Parvovirus B19 is common - adults feel worse than children

Tuberculosis (Poncet's disease)

• Mycobacterium tuberculosis
• Elderly, residing in endemic country, immunosuppressed patients, alcoholics and drug users are at risk
• Pulmonary or visceral TB an acute symmetrical polyarthritis can occur - presumably reactive, typically large joints
• Resolves after treatment for TB initiated
• Actual infection of the joint with TB can occur but this is typically monoarthritic