Paediatric Rheumatology and Allergology
Questions here test the recognition of juvenile idiopathic arthritis and vasculitis, and the management of anaphylaxis, which is the single most examined emergency in the domain. Examiners look for the correct drug, route, dose and sequence.
Anaphylaxis
- Recognise: acute onset with skin or mucosal involvement plus respiratory compromise or hypotension, or isolated hypotension after a known allergen.
- Adrenaline 1 mg/mL intramuscularly into the anterolateral thigh, 0.01 mg/kg, maximum 0.5 mg; repeat every 5 minutes as needed.
- Position supine with legs raised, give high-flow oxygen and rapid crystalloid for hypotension; remove the trigger.
- Antihistamines and steroids are adjuncts only and must never delay adrenaline. Observe 6-12 hours because of biphasic reactions.
Juvenile idiopathic arthritis
Persistent arthritis (swelling, or two of: limitation, pain, warmth) for at least 6 weeks in a child under 16 years. Subtypes: oligoarticular (young girls, uveitis risk, slit-lamp screening), polyarticular, systemic (quotidian fever, evanescent rash, arthritis), enthesitis-related and psoriatic. First line is a non-steroidal anti-inflammatory drug; methotrexate and biologics for persistent disease. Uveitis is often asymptomatic, so ophthalmological screening is mandatory.
Vasculitis and other conditions
Henoch-Schonlein purpura: palpable purpura on the legs and buttocks, abdominal pain, arthralgia, nephritis; monitor urine for 6 months. Kawasaki disease is covered with infectious disease but is a rheumatological emergency. Systemic lupus erythematosus presents with malar rash, cytopenias, low complement and nephritis.
Allergy testing
Skin prick tests and specific IgE are useful; IgG food panels are not. Cow's milk protein allergy is diagnosed by elimination and reintroduction, not by testing. Oral food challenge is the reference standard. Drug allergy labels should be verified because mislabelling drives the use of inferior antibiotics.
Worked example
A 6-year-old with known peanut allergy develops urticaria, wheeze and hypotension minutes after eating. Give intramuscular adrenaline immediately, lay the child flat with legs raised, give oxygen and a 20 mL/kg fluid bolus, and repeat adrenaline at 5 minutes if needed. Antihistamine is given after adrenaline, and the child is observed for at least 6 hours.
Traps
Giving antihistamine before adrenaline; using the subcutaneous route; sitting a hypotensive child upright; relying on IgG food panels; omitting slit-lamp screening in JIA.