Immunocompromised Host Flashcards
Why is immunodeficiency an unmet clinical problem?
Due to the large spectrum of primary immunodeficiencies (PIDs) and the failure to recognise them.
What makes an immunocompromised host?
A state in which the immune system is unable to respond appropriately and effectively to infectious microorganisms. This is caused by defects in one or more components on the immune system (more serious if adaptive immunity defect).
A host may be immunocompromised from a PID or a secondary immunodeficiency, explain the difference.
A PID is congenital and due to an intrinsic gene defect (~275 genes); it could be a missing protein, cell or a non functioning component.
A SID is acquired and due to an underlying disease/treatment (decreased production/function or increased loss/catabolism of immune components).
What is the acronym for identifying the infections suggesting immune deficiency?
SPUR: severe, persistent, unusual, recurrent (not necessarily all at once).
Recognition and diagnosis of PIDs have 10 warning signs for children and adults, give 2 examples.
A family history of PID and persistent thrush etc.
Describe 3 limitations of the 10 warning signs for PID.
For general use, it has a lack of population-based evidence (some warning signs more useful in certain cases, not in others).
PID patients have different defects and so presentations, depending on which components are affected, also some infections are subtle).
It doesn’t acknowledge the non-infectious manifestations for PID patients: autoimmunity, malignancy, inflammatory respiration).
Are patients with a PID likely to get malignancies?
YES, lymphoma happens quite a lot, but is not specific.
There are 4 classes of PID, which type is the most common?
Antibody deficiencies e.g. Common variable immunodeficiency (CVID), Bruton’s disease (X-linked) and IgA deficiency, which is often symptomatic unless there are also others, such as IgG deficiency.
There are 4 classes of PID, other than antibody deficiencies, what are there (give examples)?
Combined B and T cell, including SCID (severe combined immunodeficiency).
Phagocytic defects, with neutrophils deficient or alternatively defective e.g. X-linked common granulomatous disease (CGD).
Others.
The age for symptom onset for those suffering with a PID, can give a clue as to the type of deficiency present, how?
<6 months suggests it’s T cell or phagocyte, 6 months - 5 years means B cell/antibody or phagocyte and 5 years+ (well into adulthood), suggests B cell/antibody/complement or a secondary immunodeficiency.
You have to rule out organ abnormalities for diagnosis.
As well as age of onset of symptoms, presentation of PID type can be helped by the type of microbe doing the infecting or the site. How is this the case for defects of antibodies and complement?
Antibody defects - Strep. and Staph., sinorespiratory, arthropathies, GI (Giardia lamblia), malignancies and autoimmunity.
Complement defects - pyogenic, meningitis/sepsis/arthritis, angiooedema, encapsulated bacteria.
As well as age of onset of symptoms, presentation of PID type can be helped by the type of microbe doing the infecting or the site. How is this the case for defects of phagocytes and T cells?
Phagocytic defects - S. aureus, skin/mucous infections, deep-seated, invasive fungi (candida, Aspergillus).
T cell defects - similar to antibodies (as B cells can’t function without T, e.g. SCID), plus intracellular bacteria, all viruses and lots of everything. If untreated, leads to death, can’t thrive, deep skin and tissue abscesses, as well as opportunistic infections.
In the case of Bruton’s disease, why might symptoms not show until 3 months?
It is an X-linked antibody deficiency disease and at first the baby might be protected by maternal immunity in the form of the mother’s antibodies.
How may chronic granulomatous disease (CGD) present?
Skin infections and pulmonary Aspergilliosis (fungal).
There should be supportive management of PIDs, how?
Infection prevention (prophylactic antimicrobials), treat infections promptly and aggressively (passive immunisation), nutritional support (vitamins D and A), only use UV-radiated CMVneg blood products and avoid live attenuated vaccines if severe (as in the case of SCID).
