Lecture 15 - Septic Arthritis and Rheumatic Fever

Question 1

M protien?

Answer 1

used in differentiating Grp A streptococcal types, virulence factor, resistance to phagocytosis

Question 2

Septic arthritis?

Answer 2

occurs most frequently in childhood, fever and malaise, swelling and tenderness around affected joint, clinically joint is held in position with most intracapsular volume

Question 3

Why children?

Answer 3

unfused growht plates, highly vascular

Question 4

Septic arthritis diagnosis?

Answer 4

difficult, early diagnosis prevents irreversible damage to growth plates, lower extremities most common, staph. aureus and strep. pyogenes, drainage and washout required for treatment and diagnosis, IV antibiotics initiall, and thn long course (2-3wk)

Question 5

Acute rheumatic fever?

Answer 5

auto-immune infection following strep. pyogenes pharyngitis, generalised inflammation, rheumatic heart disease complication (mitral and/or aortic valves), several week latent period before symtpoms

Question 6

Major diagnosis criteria of ARF?

Answer 6

carditis, polyarthritis, sydenhams chorea, rash, nodules PLUS evidence of preceding strep infection (elevated antibodies or positive gram A throat culture)

Question 7

Heart diagnostics of rheumatic fever?

Answer 7

elongated PR interval (from carditis), murmer (mitral regurgitation), painful polyarthritis (typically asymmetrical and migratory)

Question 8

Movement disorder?

Answer 8

Sydenhams chorea, inability to stop moving, darting tongue, auto antibody-mediated neuronal cell-signalling in cerebrospinal fluid

Question 9

Erythema marginatum?

Answer 9

rare, characteristic skin rash, on limbs not face, spread outwards in circular shape edges raised centre clears, symptom free commonly unnoticed

Question 10

Cause of autoimmune response?

Answer 10

similarity of human cardiac myosin and streptoccocal M protein, antibodies cross react with collagen or cardiac valvular endothelia antigens then T cells infiltrate causing inflammation (arthritis) and then long term damage (carditis and ARF)

Question 11

Reccurent attacks?

Answer 11

after initial ARF attack and carditis, valves scar and nevascularise which perpetuates disease, this is why preventing recurrencies is essential

Question 12

Diagnosis?

Answer 12

negative throat culture does not rule out, nor does positive culture mean infection, ASO and anti-DNase B titres measured, highest 3-6 wk after infection and months to decline

Question 13

Protective methods following diagnosis?

Answer 13

2wk bed rest, monitor systemic inflammation, throat swab family, educate, I.M. penicillin every 4wk for decade

Question 14

Penicillin action?

Answer 14

resembles NAM and binds transpeptidase (inhibitory) to destroy cell wall

Question 15

IV penicillin?

Answer 15

rapid peak, rapid clearance, used for meningitis, pneumonia and septic arthritis

Question 16

I.M penicillin (Benathine pen G)?

Answer 16

1-2% of iV peak, but measurable amount lasts 3 weeks, pain risk at site, used fro group A strep in impetigo, and prophylaxis of strep sore throat in RF

Question 17

Penicillin excretion?

Answer 17

GFR and tubular secretion

Question 18

Septic arthritis vs RF - age?

Answer 18

any age up till 10, vs school age (5-15)

Question 19

SA vs RF - physiology?

Answer 19

active infection arthritis due to aureus and pyogenes infection of joint capsule, vs. multisystem inflammatory disease (heat, skin, brain involvement)

Question 20

SA vs RF - treatment?

Answer 20

cleaning joint and penicillin to clear infection, vs. long term penicillin to prevent recurrence