Infection & Immmunity - Allergy/HIV/Immunodeficiency/Other Flashcards
Why do allergic reactions occur?
when individuals make an abnormal immune response to harmless environmental stimuli (usually proteins)
developing immune system must be sensitised to an allergen before allergic immune response develops
How are allergic reactions classified?
IgE mediated
non-IgE mediated
What are the stages of an IgE mediated reaction?
Early phase - within minutes of exposure to allergen, caused be release of histamine and other mediates from mast cells (angioedema, urticarial etc)
Late phase - after 4-6 hours (nasal congestion, cough, bronchospasm)
How does a non-IgE mediated allergic reaction present?
delayed onset of symptoms and more varied clinical course
What are common allergens?
inhalant allergens - house-dust mite, plant pollens
ingestant allergens - nuts, seeds, legumes, cows milk
insect sting/bites, drugs etc
How do allergic reactions present?
- Mouth breathing (poss due to obstructed nasal airway from rhinitis)
- Allergic salute – habitual rubbing of nose
- Pale + swollen inferior nasal turbinates
- Hyperinflated chest or Harrison sulci from chronic undertreated asthma
- Atopic eczema affecting limb flexures
- Allergic conjunctivitis (may also be prominent creases + blue-grey discolouration below lower eyelids)
How are food allergies investigated?
- Skin-prick tests
- Measurement of specific IgE antibodies in blood
- Endoscopy + intestinal biopsy if suspect non-IgE mediated
- Exclusion of relevant food under dietician’s supervision, followed by double-blind placebo-controlled food challenge
How are allergies managed?
avoid food
antihistamines form mild attack
epipen for severe
What are some common allergens/allergic conditions?
- Eczema + food allergy usually in infancy
- Allergic rhinitis + conjunctivitis + asthma most often in preschool + primary school years
- Rhinitis + conjunctivitis often precede
How is allergic rhinitis and conjunctivitis treated?
- 2nd-gen non-sedating antihistamines (topical or systemic)
- Topical corticosteroid nasal/eye preparations
- Cromoglycate eye drops
- Leukotriene receptor antagonists e.g. montelukast
- Nasal decongestants (use for no more than 7-10 days)
- Allergen immunotherapy – sublingual or subcut
How is urticarial rash treated?
2nd-gen non-sedating antihistamines (topical or systemic)
How do you report drug reactions?
•Drug challenge is the only way to conclusively confirm an allergy (contraindicated after severe reaction)
Report severe drug reactions with yellow card scheme
How are drug reactions immediately treated?
- Assess: hospital/primary care/specialist advice
- Stop use if reaction serious, avoid use in future
- Consider alternative drug therapy
- Consider altering dose or temporarily stopping drug treatment
- Consider effects of drug interactions
- Consider possibility of withdrawal effects if drug treatment stopped suddenly
- Manage symptoms of reaction
How prevalent is HIV?
2 million children worldwide
What are the short term risks of HIV?
Opportunistic infections - TB, pneumocystis pneumonia, toxoplasmosis, VZV, CMV, candida
Thombocytopenia, anaemia, neutropenia
What are the long term risks of HIV?
Compliance Failure to thrive Risk of transmission HIV encephalopathy Neuropathy and myelopathy Cancers - Kaposi's Sarcoma, non-Hodgkins Lymphoma
What are the clinical features of infectious mononucleosis?
fever malaise tonsillopharyngitis lymphadenopathy petechiae on soft palate hepatospenomegaly maculopapular rash jaundice
What are the complications for infectious mononucleosis?
symptoms persist for 1-3 months but ultimately resolve (self limiting)
complications: hepatitis jaundice mild thrombocytopenia haemolytic anaemia upper airway obstruction to tonsil hypertrophy splenic rupture chronic fatigue syndrome neuro complications
What are the treatment options for infectious mononucleosis?
compromised airway - corticosteroids
group A streptococcus in tonsils - penicillin
What is Kawasaki disease?
systemic vasculitis fever of 38+ for more than 5 days and 4+ of the following: - conjunctival infection in both eyes - change in mouth/throat - changes to skin on arms or legs - rash - swollen LN of neck
What are the 3 phases of Kawasaki disease?
1.Acute (weeks 1-2)
•Sudden symptoms + severe
2.Sub-acute (weeks 3-4)
•Symptoms severe but last longer
•Fever subsides but persistent irritability + considerable pain
•Complications likely
3.Convalescent (weeks 4-6)
•Recovery + all signs of illness should disappear
•May still lack energy
•Some complications
What are the investigation results for Kawasaki disease?
CRP, ESR, WCC = raised
Platelet count - rises in the 2nd week
Echo - to check for aneurysms
What is the treatment for Kawasaki disease?
- IV immunoglobulin (within first 10 days, reduce risk of coronary artery aneurysms)
- Aspirin – reduce risk of thrombosis (high dose until fever subsides + low dose until echo at 6 weeks)
- Antiplatelet aggregation agents if platelet count v high
- Long term warfarin + close follow up if giant coronary artery aneurysms
- If persistent inflammation + fever, treat with infliximab, steroids or ciclosporin
What are the long term complications of Kawasaki disease?
aneurysms of coronary arteries
subsequent narrowing from vessels from scar formation can result in myocardial ischaemia and sudden death
What are the causes of immunodeficiency in children?
Deliberate immunosuppression - BM transplant, organ transplant, crohn’s disease
Non-deliberate immunosuppression - malnutrition, ageing, cancers
What are the causes immunodeficiency in children?
Primary = intrinsic defects in immune system T cell defects B cell defects Neutrophil defects Leucocyte function defects Complement defects
Secondary - another disease or treatment e.g. HIV
How can infection be prevented in immunocompromised children?
- Antimicrobial prophylaxis
- Antibiotic treatment – prompt treatment of infections, generally longer courses with lower threshold for IV
- Screen for end organ disease
- Immunoglobulin replacement therapy (for children with antibody deficiency)
- Bone marrow transplantation (for SCID + chronic granulomatous disease
- Gene therapy (certain forms of SCID but risk of leukaemia)
What are the clinical features of Typhoid fever?
- Worsening fever
- Headaches
- Cough
- Abdo pain
- Anorexia
- Malaise
- Myalgia
- GI symptoms later
- Poss splenomegaly, bradycardia + rose-coloured spots on trunk
What is the treatment of typhoid fever?
3rd gen cephalosporin or azithromycin
What are the clinical features of malaria?
fever dairrhoea vomiting flu-like symptoms jaundice anaemia thrombocytopenia rare cerebreal malaria
onset is 7-10 days after inoculation but iinfections can present many months later
How is malaria treated?
Quinine
Travellers should use prophylaxis
