Scarlet Fever

Question 1

What is scarlet fever caused by?

Answer 1

Group A haemolytic streptococci

Question 2

Give an example of a group A haemolytic streptococci causing scarlet fever

Answer 2

Streptococcus pyogenes

Question 3

Age of incidence

Answer 3

2-6 years

Question 4

Symptoms of scarlet fever

Answer 4

Fever up to 2 days
Malaise
Headache
Nausea
Vomiting
Strawberry tongue
Pharyngitis
Cervical lymphadenopathy

Rash - on torso, spares feet and palms - sandpaper pinpoint appearance

Question 5

Diagnosis of scarlet fever

Answer 5

Throat swab but start antibiotics immediately

Question 6

Management of scarlet fever

Answer 6

Oral penicillin for 10 days
Or azithromycin if allergic
Can return to school after 24 hours of taking antibiotics

Notifiable disease

Question 7

Common complications of scarlet fever

Answer 7

Otitis media - ear infection
Rheumatic fever - 20 days after infection
Acute glomerulonephritis - 10 days after infection
Invasive - bacteremia, mengitis, necrotizing fascitis

Question 8

Rheumatic fever - definition and pathophysiology

Answer 8

Rheumatic fever is an autoimmune attack on the heart, nerves and joints after a throat infection. Group A strep contains M antigens. B lymphocytes make antibodies against these M antigens. These M antigens look like self antigens.

Question 9

What is it called when the group A strep pretends to be self antigens?

Answer 9

Molecular mimicry

Question 10

Give examples of self antigens/tissues which lead to cross reaction of anti-M antibodies and thus rheumatic fever

Answer 10

Cardiac myosin
Laminin
Neuronal
Subcutaneous molecules
Dermal tissues

Question 11

What type of reaction occurs as a result of cross-reaction?

Answer 11

Type 2 hypersensitivity reaction

Question 12

Symptoms/signs of rheumatic fever

Answer 12

Fever above 39 degrees
Migrating polyathritis
Carditis - chest pain, dyspnea, palpitations, mitral regurg
Nodules - collagen collections on extensor surfaces
Erythema marginatum
Sydenham’s chorea - involuntary jerking muscle movements

Question 13

Diagnostic criteria for rheumatic fever

Answer 13

Jones criteria

Question 14

Jones criteria - major

Answer 14

Joint pain
O-carditis
Nodules
Erythema marginatum
Sydenham’s chorea

Question 15

Minor criteria of the Jones Criteria

Answer 15

CRP above 3mg/dL
Arthralgia
Fever above 38 in high risk groups/above 38.5 in low risk groups
ESR above 60 or above 30 in high risk groups
Prolonged PR interval
Anamnesis
Leukocytosis

Question 16

What counts as Jones positive?

Answer 16

Evidence of Group A strep + two major criteria
or 1 major and 2 minor

(note that chorea does not require evidence of GAS)

Question 17

Investigations for rheumatic fever

Answer 17

ECG
CXR
Echo
Throat culture

Serology for Anti-streptolysis O (ASO) and Anti-deoxyribonuclease B

Question 18

Treatment of rheumatic fever

Answer 18

Mainly symptomatic relief and prophylaxis as manifestations resolve (but carditis might not)

Pain relief - paracetamol
Avoid NSAID as may mask joint pain
Antibitoics - benzathine benzylpenecillin
Cardiits - ACEi, diuretics
CHorea - carbamazepine, valproic acid

Question 19

Prophylaxis for rheumatic fever

Answer 19

Benzathine benzylpenecillin every 3-4w or azithromycin if allergic