Immuno: Malabsorption CPC Flashcards
(36 cards)
List three causes of microcytic anaemia.
- Iron deficiency
- Thalassaemia trait
- Anaemia of a chronic disease
Iron studies to differentiate microcytic anaemia
What is anisopoikilocytosis and which type of anaemia is it associated with?
- Variations in size and shape of cells
- Associated with iron deficiency anaemia (and thalassaemia trait to a lesser degree)
What is basophilic stippling? List some causes.
- Basophilic appearance of red blood cells caused by the presence of aggregated ribosomal material
Causes:
beta-thalassaemia trait
lead poisoning
alcoholism
sideroblastic anaemia
Which condition do hypersegmented neutrophils tend to be present in?
Megaloblastic anaemia - due to impaired DNA synthesis
List some causes of megaloblastic anaemia.
- B12 deficiency
- Folate deficiency
- Drugs
In which conditions might you see target cells (codocytes)?
- Iron deficiency
- Thalassaemia
- Hyposplenism
- Liver disease
NOTE: target cells have a high SA: V ratio
What are Howell-Jolly bodies? Which condition are they associated with?
- Nuclear remnants present within red blood cells
- Present in hyposplenism, as these remnants are normally removed by the spleen
List some causes of iron deficiency.
- Blood loss (major cause)
- Poor diet
- Malabsorption
- Combinations of the above
iron deficiency anemia blood film features
hypochromic, microcytic
anisopoikilocytosis
megaloblastic anaemia blood film features
hypersegmented neutrophils
macrocytes
hyposplenism blood film features
Target cells
Howell jolly bodies
List some causes of B12 and folate deficiency.
- Poor diet
- Malabsorption
- Pernicious anaemia
List some causes of hyposplenism.
Absent spleen:
* therapeutic
* trauma
Poorly-functioning spleen:
* inflammatory bowel disease
* Coeliac disease
* sickle cell disease
* SLE
Which deficienceies are typically seen in Coeliac disease?
- Iron
- B12
- Folate
- Fat
- Calcium
Which deficiencies are typically seen in Crohn’s disease?
- B12
- Bile salts
Which deficiencies are typically seen in pancreatic disease?
- Fat
- Calcium
- B12
Which investigatio are typically performed in Coeliac disease?
- CRP, ESR, Faecal elastase
- Serological tests
- Upper GI endoscopy and distal duodenal biopsy (GOLD STANDARD)
Which gene locus does the heritability of coeliac disease tend to frequently map to?
MHC complex gene loci
Which HLA alleles are particularly common in patients with coeliac disease?
- HLA-DQ2 (80%) - DQA1*0501 and DQB1*02 alleles
- HLA-DQ8
polygenic autoimmune
Describe the T cell response to gluten in coeliac disease.
- Peptides from gluten (gliadin) are deamidated by tissue transglutaminase
- Deamidated gliadin is taken up by antigen-presenting cells and presented via HLA molecules to CD4+ T cells
- CD4+ T cell activation results in secretion of IFN-gamma and may increase IL-15 secretion
- These cytokines promote activation of intra-epithelial lymphocytes (gamma-delta T cells)
- The intraepithelial lymphocytes will kill epithelial cells via the NKG2D receptor (normally recognises the stress protein MICA)
Describe the B cell response to gluten in coeliac disease.
- B cells will process gluten antigens and present it via HLA molecules to CD4+ T cells
- The primed T cells will provide help to the B cells via CD40L: CD20 to allow B cells to undergo germinal centre reactions
- B cells undergo isotype switching and affinity maturation to become memory cells and plasma cells which produce antibodies against gliadin
Which auto-antibodies may be tested when investigating coeliac disease?
anti TTG (most specific) and anti EMA
(antibodies against deaminated gliadin peptide is an old + non specifc test)
if +ve –> do an endoscopy + duodenal biopsy to confirm diagnosis
What important test should be performed before checking anti-tTG and anti-endomysial antibody levels?
- IgA levels
- IgA deficiency can produce false-negative results
