Week 10 - The Immunocompromised Host Flashcards
What is an immunocompromised host?
A state in which the immune system is unable to respond appropriately and effectively to infectious microorganisms
How can you recognise immunodeficiency?
Infections that are:
- Severe
- Persistent
- Unusual
- Recurrent
How can you classify immunodeficiency diseases?
- Primary ID = intrinsic defect
- – Severe combined immunodeficiency (SCID)
- – Occur in the first months of life
- – 70% male – X-linked
- – 80% patients are
How can you classify primary immunodeficiency diseases?
According to which immune component is defective
- B cell (most common)
- – E.g. inability of B cells to mature into plasma cells
- – E.g. B cell unable to switch to IgA
- T cell
- – E.g. stem cell defect
- – E.g. death of developing thymocytes
- – E.g. defective T cell development
- Phagocytes
- – E.g. adhesion to endothelium
- – E.g. Lack of respiratory burst
- – E.g. failure of phagolysosome formation
- Complement
- – E.g. hereditary angioedema
What are the different types of secondary immunodeficiency diseases?
- Decreased production of immune components
— Malnutrition
— Infection (E.g. HIV)
— Liver diseases
— Lymphoproliferative diseases
— Splenectomy
• Causes: infarction, trauma, infiltration, autoimmune haemolytic disease, coeliac disease, congenital - Increased loss or catabolism
— Protein-losing conditions (e.g. nephropathy, enteropathy)
— Burns
What is the immune function of the spleen?
- Bloodborne pathogens
- – Encapsulated bacteria
- Antibody production
- – Acute response: IgM prodution
- – Long term protection: IgG production
- Splenic macrophages:
- – Removal of opsonised microbes
- – Removal of immune complexes
How do apslenic/splenectomised patients present and how can you manage them?
Presentation:
- Increased susceptibility to encapsulated bacteria
— E.g haemophilus influenzae, streptococcus pneumoniae, neisseria mengitidis
- Overwhelming post-splenectomy infection
Management:
- Penicillin prophylaxis (lifelong)
- Immunisation against encapsulated bacteria
- Medic alert bracelet
How do patients with defective B cells present?
- Recurrent upper and lower respiratory bacterial infections
- – Leads to bronchiectasis
- GI complications
- – Includes infections (Giardia)
- Arthropathies
- – Including mycoplasma/ureaplasma
- Increased incidence of autoimmune disease
- Increase incidence of lymphoma and gastric carcinoma
How do you manage patients with defective B cells?
- Prompt/prophylactic antibiotics
- Immunoglobulin replacement therapy
- – Goal: serum IgG > 8g/L
- – Lifelong treatment
- Management of respiratory function
- Avoid unnecessary exposure to radiation
How do patients with defective phagocytes present?
Prolonged and recurrent infections:
- Skin and mucous membranes (ulcers)
- Osteomyelitis, sepsis
- Deep abscesses
- Commonly staphylococcal
- Invasive aspergillosis
- Inflammatory problems
How do you manage patients with defective phagocytes?
- Prophylactic antibiotics/anti-fungal agents/immunisation
- Surgical management
- Interferon-g
- Steroids
- Stem cell transplantation
Consider aspergillus as a cause of fungal infection in the immunocompromised
- Aspergillus can be found in dusty buildings
- It is a fungus
- It usually causes a lung infection
- Patients can present with no symptoms, or they may cough up blood
— If severe, may cause:
• Cough
• Fever
• Chest pain
• Difficulty breathing - Can spread to other organs
— Kidney failure
— Liver failure
— Breathing difficulties - Can be treated with amphotericin
— An anti-fungal agent
Discuss varicella zoster infection
- Primary infection causes chickenpox
- – Causes an itchy, blister-like rash on the skin
- Lays dormant in the dorsal horn
- Can affect the dermatomes, causing shingles
- – Recurrent infection = shingles
- – More likely to occur if immunocompromised, but fairly common
How do patients with severe combined immunodeficiency disease present?
- Failure to thrive
- Deep skin and organ abscesses
- Low lymphocyte count
- High susceptibility to bacterial, fungal and viral infections
- – Pneumocystis pneumonia
- – Varicella-zoster virus
- – Cytomegalovirus
- – Epstein Barr virus
How do you manage patients with severe combined immunodeficiency disease?
- Fatal if not treated
- Short term:
— No live vaccines
— Only irradiated, CMV-negative blood products
— Aggressive treatment of infections
— Prevention of new infections
• Reverse barrier nursing/laminar flow
• Prophylactic antibiotics and anti-fungals
• IV-immunoglobulin - Long term:
— Bone marrow/stem cell transplantation
— Gene therapy
