septic arthritis and rheumatic fever

Question 1

describe how septic arthritis occurs and its symptoms

Answer 1

• infection from bacteria in bone, bone marrow and/or joint space
• most frequently in childhood as bone is more vascular
• fever, malaise
• swelling, erythema, tenderness around joint
• individual holds joint in position that maximises intracapsular volume e.g. knee flexed

Question 2

examination of septic arthritis

Answer 2

• knee joint easily examined/palpated

- plain Xray used to rule out other causes

Question 3

management of septic arthritis

Answer 3

• joint washouts (to remove pus)
• IV antibiotics (2-3 weeks)
• then oral amoxycillin (1 week)

Question 4

common pathogens causing septic arthritis

Answer 4

1 = S. aureus

then S. pyogenes

Question 5

describe acute rheumatic fever

Answer 5

is an auto-immune response following throat infections (pharyngitis) with strep pyogenes

• causes generalised inflammation
• attacks certain parts of the body e.g. heart, joints, brain
• can cause damage to mitral/aortic valves = RHD

Question 6

timeline of RF

Answer 6

• throat infection with group A strep
  (red, swollen tonsils with exudate)
• latent period for several weeks

Question 7

describe how jones criteria diagnosis RF

Answer 7

diagnosis made with combination of major and minor criteria

• e.g. 2 major or 1 major + 2 minor

and evidence of preceding strep infection

Question 8

what falls under the major jones criteria

Answer 8

• carditis
• polyarthritis
• sydenhams chorea
• erythema marginatum

Question 9

what falls under the minor jones criteria

Answer 9

• fever
• polyarthralgia
• history of RF
• raised acute phase proteins (CRP, ESR)
• prolonged PR interval

Question 10

arthritis in RF

Answer 10

• commonest symptom
• typically extremely painful, unable to bear weight
• large joint usually affected
• poly arthritis is asymmetrical, migratory

Question 11

sydenhams chorea

Answer 11

• dance-like movements
• clumsy
• fidgeting
• hypotonia

Question 12

mechanism of ARF

Answer 12

occur from autoimmune mechanisms related to molecular mimicry

• normal host response to group A strep produce antibodies to bacterial antigen
• production of cross-reactive antibodies gives immune recognition to both pathogen and host cells
  - attacks cardiac myosin, collagen of joints, heart valve endothelium

Question 13

ARF causing RHD

Answer 13

• recurrent RF attacks due to repeal infections leads to scar formation on valves
• valvular scars and new vessels gives a ‘floppy’ valve ==> mitral/aortic regurgitation

Question 14

streptococcal antibody titres

Answer 14

important part in confirming diagnosis
- most RF cases don’t culture positive throat

tests used are plasma ASO and anti-DNase B titres
- ASO titre levels highest around 3-6 weeks after infection

Question 15

management of ARF

Answer 15

• bed rest in hospital for 2 weeks
• monitor systemic inflammation (weekly CRP, ESR)
• family members swabbed and treated
• education
• IM penicillin every 4 weeks for next 10 years

Question 16

whats the difference between septic arthritis and ACF

Answer 16

septic arthritis
- any age group
- acute active infection-arthritis due to bacteria and pus in joint
(S. aureus and S pyogenes)

ARF

• school age 5-10
• autoimmune antibody response to S pyogenes
• multisystem inflammatory disease
• penicillin used long term to prevent recurrence