S9 Immunocompromised Host Flashcards
(34 cards)
What is an immunocompromised host?
A state in which the immune system is unable to respond appropriately and effectively to infectious microorganisms
Due to a defect in one or more components of the immune system
What are the two main types of immunodeficiency?
Primary - congenital - due to a gene defect
Secondary - acquired - due to an underlying disease/treatment
What 3 questions need to be considered about components of the immune system that lead to an immunocompromised host? (To specify what type of deficiency it is)
Is the component present?
Is it in the correct number?
Is it functional?
When do you suspect immunodeficiency?
If the infection is… SPUR
Severe
Persistent
Unusual
Recurrent
What are the 10 warning signs of primary immunodeficiency in children?
- 4+ new ear infections within a year
- 2+ serious sinus infections within a year
- 2+ months on antibiotics with little effect
- 2+ pneumonia’s within a year
- Failure to gain weight/grow normally
- Recurrent, deep skin or organ abscesses
- Persistent thrush in the mouth/fungal infection on the skin
- Need IV antibiotics to clear infections
- 2+ deep-seated infections inc. septicaemia
- Family history of PID
How do the warning signs of primary immunodeficiency vary in adults compared to children?
- 2+ new sinus infections within a year without allergy
- chronic diarrhoea with weight loss rather than growing normally
- recurrent viral infections
- persistent thrush/fungal infection elsewhere as well as skin
- infection with harmless TB like bacteria
What are the limitations of the 10 warning signs?
- lack of population based evidence
- everyone is different with different defects and presentations
- some primary immunodeficiency patients have had non-infectious manifestations like malignancy
What are most immunodeficiencies caused by?
Antibody defects (about 65%)
What are the common types of immunodeficiency antibody defects?
Defects in B cell development
* x-linked agammaglobulinaemia - Bruton’s disease
Defects in antibody production
- common variable immunodeficiency (CVID)
- selective IgA deficiency
- hyper-IgM syndrome
What is the significance of selective IgA deficiency?
Those with this deficiency can develop anti-IgA antibodies that means any treatment with IgA results in destruction of the IgA
What are the common types of immunodeficiency T cell defects?
Combined B and T cell defects
* severe combined immunodeficiency (SCID)
T cell defects
* Di George syndrome (thymus)
Why do you get combined B and T cell defects?
Need T helper cells for B cells to produce antibodies e.g. IgM
What are the common types of immunodeficiency phagocytic defects?
Defects in respiratory burst
* chronic granulomatous disease (CGD)
Based on age, when do each type of primary immunodeficiency present with symptoms?
If onset is younger than 6 months it is highly suggestive of T-cell or phagocyte defects
If onset is over 6 months but under 5 years this is suggestive of B-cell, antibody or phagocyte defect
If onset is over 5 years this is suggestive of B-cell/antibody/complement or secondary immunodeficiency
Why don’t children under 6 months present with symptoms when they have B-cell or antibody defects?
Because up to 6 months, they have maternal IgG antibodies
What is the main cause of secondary immunodeficiency?
Malnutrition
What types of microbes are people more susceptible to with complement defects? What infections do they cause?
Neisseria species e.g. meningitis/STDs, H. influenzae, Streptococci - encapsulated bacteria
Cause pyogenic infections, meningitis, sepsis, arthritis, angioedema
What types of microbes are people more susceptible to with phagocytic defects? What infections do they cause?
- Staphylococcus aureus (cellulitis), Pseudomonas aeruginosa (cystic fibrosis)
- Candida species, Aspergillus species
Skin/mucous infections, deep seated infections, invasive fungal infection (aspergillosis)
What types of microbes are people more susceptible to with antibody defects? What infections do they cause?
- Streptococci, Staphylococci
- enteroviruses
- Giardia lamblia
Infections at mucosal sites - sino-respiratory infections, GI infections, malignancies
What types of microbes are people more susceptible to with T-cell defects? What infections do they cause?
- encapsulated and intracellular bacteria e.g. Salmonella typhi
- all viruses
- Candida species, Aspergillus species
- Toxoplasma gondii, Cryptosporidium parvum
Death if not treated, deep skin and tissue abscesses, opportunistic infections
ALL TYPES OF MICROBES
What do people with chronic granulomatous disease (CGD) present with?
- pulmonary aspergillosis
* skin infections
If the condition effects women more then men in the family, which immunodeficiency is it likely to be?
Bruton’s disease (B cell deficiency)
What supportive treatments are suggested for PIDs?
- infection prevention - prophylactic antimicrobials
- treat infections quickly and aggressively
- nutritional support e.g. Vits A and D
- avoid live vaccines in patients with severe PIDs like SCID
- use specific safe blood products only
What specific treatments are suggested for PIDs?
- regular immunoglobulin therapy
* haematopoietic stem cell therapy (for SCID)
