S10) The Immunocompromised Host Flashcards
What is an immunocompromised state?
An immunocompromised state is a state in which the immune system is unable to respond appropriately and effectively to infectious microorganisms
What causes an immunocompromised state?
A defect in 1/more components of the immune system
What are the two different types of immunocompromised states?
- Primary immunodeficiency (congenital)
- Secondary immunodeficiency (acquired)
Describe the congenital causes of primary immunodeficiency
Due to intrinsic gene defect:
- Missing protein
- Missing cell
- Non-functional components
Describe the acquired causes of secondary immunodeficiency
Due to an underlying disease/treatment:
- ↓ Production/function of immune components
- ↑ Loss/catabolism of immune components
When do we suspect an immunodeficiency?
Infections suggesting underlying immune deficiency:
- Severe
- Persistent
- Unusual
- Recurrent
Identify 5 warning signs for PID in adults
- Chronic diarrhoea (+ weight loss)
- Recurrent viral infections (warts, herpes, colds)
- Recurrent need for IV antibiotics to clear infections
- Persistent thrush/fungal infections
- Family history of PID
Identify 5 warning signs for PID in children
- Family history of PID
- Need for IV antibiotics to clear infections
- Failure to gain weight / grow normally
- Recurrent deep skin/organ abscesses
- Persistent thrush in mouth / fungal infection on skin
What are the limitations of the warning signs for PID?
- Lack of population-based evidence: family history, failure to thrive, sepsis (IV antibiotics)
- Patients with different defects/presentations (infections with a subtle presentation)
- Patients with non-infectious manifestations: autoimmunity, malignancy, inflammatory responses
Identify some primary immunodeficiency diseases of clinical importance
- Bruton’s disease (X-linked agammaglobulinaemia)
- Common variable immunodeficiency (CVID)
- Severe combined immunodeficiency (SCID)
- Chronic granulomatous disease
Describe the presentation of PIDs in terms of the age of symptom onset
- Onset < age 6 months suggests a T-cell / phagocyte defect
- Onset = 6 months suggests a B-cell, antibody / phagocyte defect
- Onset > 5 years old suggests a B-cell, antibody / complement defect or an SID
How do PIDs due to a complement deficiency present?
- Pyogenic infections (C3)
- Meningitis / sepsis / arthritis (C5-C9)
- Angioedema (C1 inhibitor)
How do PIDs due to a phagocytic defects present?
- Skin/mucous infections
- Deep seated infections
- Invasive fungal infection (aspergillosis)
How do PIDs due to an antibody deficiency present?
- Sinorespiratory infections
- Arthropathies
- GI infections
- Malignancies
How do PIDs due to T cell defects present?
- Death if not treated
- Failure to thrive
- Deep skin and tissue abscesses
- Opportunistic infection
What is Severe Combined Immunodeficiency?
SCID is a primary immunodeficiency characterised by a severe defect in both the T- & B-lymphocytes
What is Common Variable Immunodeficiency?
CVID is a primary immunodeficiency characterised by recurrent infections and low antibody levels (specifically IgG, IgM and IgA)
What is Bruton’s disease?
Bruton’s disease is an inherited primary immunodeficiency caused by a severe block in B cell development and a reduced immunoglobulin production
What is Chronic granulomatous disease?
- Chronic granulomatous disease is an X-linked inherited primary immunodeficiency wherein the body cannot phagocytose pathogens due to difficulty forming the superoxide radical (no respiratory burst)
- This increases susceptibility to infections by bacteria and fungi
What is the diagnosis for the following clinical case?
“A 6 month-old boy was born at term physically normal and apparently healthy. In last 3 months, he has had recurrent fungal (diaper rash, oral candidiasis), viral (upper respiratory tract infections), and bacterial (otitis media) infections, all of which resolved with appropriate pharmacologic intervention
He is below the 50% percentile for weight and has weak IgG response to vaccines. Both sexes of the family have been affected by these infections.”
Severe combined immunodeficiency
What is the diagnosis for the following clinical case?
“A 12-month-old boy with 4 episodes of severe Gpos bacterial pneumonia in the last 6 months. He has had recurrent diarrhoea (Giardia lamblia) and his tonsils are barely detectable.
He is below the norm for height and weight. After the recommended paediatric immunisations show a low IgG, undetectable IgE, IgA and IgM and no B cells.
The patient has three healthy sisters aged 3, 5, and 7 years. The family lost a boy at 10 months of age to bacterial pneumonia 8 years ago.”
Bruton’s disease
What is the diagnosis for the following clinical case?
” A young patient who developed since the age of 4 weeks multiple staphylococcal abscesses in the chest, face and buttock requiring surgical incision and a course of systemic antibiotics for 10 days.
By the age of 2 he was admitted to the hospital 5 times for staphylococcal infections and pulmonary aspergillosis. Height and weight below the average
Three elder brothers had died of infections at an early age but sisters healthy. Neutrophils failed to produce oxygen radicals (respiratory burst).”
Chronic granulomatous disease
What is the diagnosis for the following clinical case?
“40 year-old women suffers with recurrent bacterial respiratory (sinusitis, otitis, tonsillitis) and GI infections (intermittent diarrhoea) throughout her life.
Both IgG, IgM, IgA are below normal. Poor IgG response to pneumococcal vaccines. Number of B cells and T cells were normal.
Mother and sister had also poor response to polysaccharide vaccines and died from haemolytic anaemia and non-Hodgkin’s lymphoma.”
Common variable immunodeficiency
Outline the management of PIDs in terms of supportive treatment
- Infection prevention (prophylactic antimicrobials)
- Treat infections promptly and aggressively (passive immunisation)
- Nutritional support (Vitamins A/D)
- UV-irradiated CMVneg blood products only
- Avoid live attenuated vaccines in patients with severe PIDs (SCID)
Outline the management of PIDs in terms of specific treatment
- Regular Immunoglobulin therapy (IVIG or SCIG)
- SCID: Hematopoietic Stem Cell therapy
Outline the management of PIDs in terms of specific treatment
- E.g. Autoimmunity and malignancies*
- Lung function assessment for organ damage
- Avoid non essential exposure to radiation
What is the goal of immunoglobulin replacement therapy?
- Serum IgG > 8g/l
- Life long treatment
Which conditions is immunoglobulin replacement therapy used for?
- CVID
- XLA (Bruton’s disease)
- Hyper-IgM syndrome
What are the different formulations in immunoglobulin replacement therapy?
- IvIg
- ScIg (young patients)
Secondary immune deficiencies involve the decreased production of immune components.
Provide some causes of this
- Malnutrition
- Infection e.g. HIV
- Liver diseases
- Lymphoproliferative diseases
- Splenectomy
Identify 6 indications for a splenectomy?
- Infarction (sickle cell anaemia)
- Trauma
- Autoimmune haemolytic disease
- Infiltration (tumour)
- Coeliac disease
- Congenital
In terms of its immune function, explain why the spleen is so important?
- Engulf bloodborne pathogens, especially encapsulated bacteria
- Antibody production
I. Acute response: IgM production
II. Long term protection: IgG production
- Splenic macrophages remove opsonised microbes & immune complexes
How does an asplenic/splenectomised patient present?
- ↑ susceptibility to encapsulated bacteria e.g. Haemophilus influenzae, Streptococcus pneumoniae and Neisseria Meningitidis
- OPSI (overwhelming post-splenectomy infection) ⇒ sepsis and meningitis
Describe the management of an asplenic/splenectomised patient
- Penicillin prophylaxis (life-long)
- Immunisation against encapsulated bacteria
- Medic Alert bracelet
Patients with a haematological malignancies have increased susceptibility to infections.
Why is this?
- Chemotherapy-induced neutropenia
- Chemotherapy-induced damage to mucosal barriers
- Vascular catheters
Describe the management of patients with haematological malignancies
- Treat suspected neutropenic sepsis as an acute medical emergency and offer empiric antibiotic therapy immediately
- Assess patient’s risk of septic complications
Secondary immune deficiencies also involve an ↑ loss/catabolism of immune components.
Provide some causes of this
- Nephropathy
- Enteropathy
- Burns
