Anemia Flashcards
Anaemia
A haemoglobin concentration lower than normal range.
Anaemia is a manifestation of an underlying disease, not a diagnosis in itself.
Koilonychia
Spoon shaped nails, caused by iron deficiency.
Angular stomatitis
Inflammation of corners of the mouth, caused by iron deficiency.
Glossitis
Inflammation and depapillation of tongue, caused by vitamin B12 deficiency.
Abnormal facial bone development
Associated with thalassemia, due to expansion of haematopoietic tissues into skull and facial bones - extramedullary haemopoiesis.
Erythropoiesis
Red blood cell production.
Erythropoietin (EPO)
Hormone produced by interstitial cells in kidney. It stimulates RBC production in the bone marrow.
In negative feedback loop ie low blood oxygen = more EPO produced by kidney and released into bloodstream = stimulates RBC production.
Therefore anaemia can result from chronic kidney disease or bone marrow’s inability to respond to EPO.
Myelofibrosis
Bone marrow infiltrated by cancer cells or fibrous tissue = number of normal haemopoietic cells is reduced.
Myelodysplastic syndromes
Rare form of blood cancer where abnormal clones of marrow stem cells limit the capacity to make red and white blood cells.
Sideroblastic anaemia
Body produces enough iron but is unable to put it into haemoglobin. Defects in haem pathway can lead to this.
Haemolytic anaemia - causes and symptoms
RBC’s are destroyed faster than they are made. Caused by either inherited factors or acquired damage.
Inherited factors eg glycolysis defect, G6PDH deficiency, Hb defect (sickle cell)
Acquired damage eg mechanical damage, heat damage (severe burns), oxidant damage
Symptoms: splenomegaly (overwork of red pulp), accu. of bilirubin = jaundice, and pigment gallstones.
Causes of haemolytic anemia
Inherited - mutations in genes coding for proteins involved in interaction between plasma membrane and cytoskeleton - cells are less flexible, more easily damaged.
They break up in the circulation or are removed more quickly by RES (spleen).
—Eg hereditary spherocytosis
Acquired damage - mechanical damage eg shear stress as cells pass through defective heart valve; cells snagging on fibrin strands in small blood vessels where increased activation of clotting cascade.
—Eg microangiopathic haemolytic anaemias
- heat damage from severe burns (dehydration)
- osmotic damage (drowning in freshwater)
Hereditary spherocytosis
Causes?
Treatment?
Inherited blood disorder where RBC’s have a spherical shape rather than a biconcave shape. They are more fragile and get stuck in capillaries as they are less flexible.
Proteins involved: ankyrin, band 3, protein 4.2, beta-spectrin, alpha-spectrin - defects in these cause disease.
Caused by mutation in a gene coding for one of these proteins, which are involved in interactions between the plasma membrane and cytoskeleton.
Splenectomy to limit the effects of the disease.
Microangiopathic haemolytic anemias
Anaemia that results from mechanical damage.
eg Shear stress as cells pass through defective heart valve; cells snagging on fibrin strands in small vessels with increased activation of clotting cascade (DIC).
Schistocytes
Fragments of RBC’s resulting from mechanical damage.
Pyruvate kinase
Catalyses intermediate of glycolysis into pyruvate; the final enzyme in glycolysis.
Pyruvate kinase deficiency
As RBC lack mito, they rely on glycolysis for energy production. Defective glycolytic pathway causes RBC to become deficient in ATP and they undergo haemolysis.
G6PDH deficiency
Catalyses glucose 6P into 6-phosphogluconate, generating NADPH. Occurs in PPP.
NADPH needed to protect against oxidative stress as NADPH is used to reduce GSSG back to 2GSH, which donates H+ and e- to ROS.
Haemolysis
Break down of RBC.
Heinz bodies
Aggregates of cross-linked haemoglobin - due to protein damage eg due to ROS.
Reticuloendothelial system (RES)
Part of immune system that consists of phagocytic cells located in reticular connective tissue - the cervical lymph nodes, diaphragm, liver, thymus, axillary lymph nodes, spleen and inguinal lymph nodes.
Intravascular/ extravascular haemolysis
Damage occurring within the blood vessels/ within the RES.
Autoimmune haemolytic anaemia
Autoantibodies bind to red cell membrane proteins, causing them to be recognised by macrophages in the spleen and are destroyed.
Thalassemia
Inherited disorders resulting from decreased or absent alpha or beta globin chain production.
Imbalance in composition of Hb alpha2 beta2 tetramer results in defective microcytic hypochromic red cells.
Microcytic
Smaller than average RBC’s due to insufficient Hb.
Hypochromic
RBC’s are less pigmented than normal, usually due to decreased Hb.
Extramedullary haemopoiesis
Formation and activation of blood cells outside bone marrow, eg in spleen and liver.
Reticulocytosis
Increase of reticulocytes in blood.
Reticulocytes
Immature RBC’s.
They have no nucleus and need to eliminate remaining mitochondria, but do have some residual RNA.
Macrocytic
RBC’s that are larger than normal.
Normocytic
RBC’s contain a lower than normal amount of Hb.
Macrocytic anaemia
Anaemias where RBC’s are larger than normal.
Megaloblastic anaemia
Interference with DNA synthesis during erythropoiesis causes development of nucleus to be retarded in relation to maturation of cytoplasm.
Cell division delayed and erythroblasts continue to grow and form megaloblasts which give rise to larger red cells.
Thymidine deficiency - in its absence, uracil is incorporated. DNA repair enzymes detect errors and constantly repair by excision
= asynchronous maturation between nucleus and cytoplasm where the nucleus does not fully mature.
Macronormoblastic erythropoiesis
Normal development of nucleus and cytoplasm but erythroblasts are larger than normal and give rise to larger RBC.
‘Stress’ erythropoiesis
High reticulocyte count, and high level of erythropoietin, which leads to expanded and accelerated erythropoiesis.
Folate
Synthetic form is folic acid.
Absorbed mainly by duodenum and jejunum. Converted to FH4 by intestinal cells. Taken up by liver which acts as a store.
Folate deficiency - causes
Caused by: poor diet; increased requirements eg pregnancy; disease of duodenum and jej; drugs eg methotrexate; alcoholism; urinary loss of folate in liver disease and heart damage.
! Folic acid taken before conception/during1st 12 weeks of pregnancy prevents most neural tube defects.
What prevents most neural tube defects in babies and why?
Folic acid
Vit B12 deficiency is associated with focal demyelination, as it is needed for myelin sheath production.
What is vitamin B12 needed for?
Required for normal erythropoiesis.
Essential for normal function and development of CNS.
Haptocorrin
*
Produced by salivary glands; protects vit B12 from acid degradation in stomach.
Receptor-mediated endocytosis
Protein on transport vesicle binds to receptor on cell
In vit B12 absorption and cholesterol absorption via LDLs.
Transcobalamin
*
Vit B12 binds to transcobalamin in blood and is transported around bloodstream.
Pernicious anaemia
A cause of vit B12 deficiency:
Decreased or absent intrinsic factor (IF) which causes progressive exhaustion of vit B12 reserves.
An autoimmune disease; 2 types of antibody - blocking Ab that blocks binding to B12 and IF; binding Ab prevents receptor mediated endocytosis.
3 most common causes of vit B12 deficiency
-Dietary deficiency
-Pernicious anaemia (lack of intrinsic factor)
-Diseases of the ileum eg Crohn’s disease
Intrinsic factor (IF)
Binds to vit B12 which is then taken up by the cell.
How do B12 and folate link?
*
Lack of B12 will ‘trap’ folate in the stable methyltetrahydrofolate form, prevents its use in other reaction eg synthesis of thymidine for DNA synthesis.
Why do B12 and folate deficiency cause megaloblastic anaemia?
Both deficiencies lead to thymidine deficiency. In its absence, uracil is incorporated. DNA repair enzymes detect errors and constantly repair by excision
= asynchronous maturation between nucleus and cytoplasm where the nucleus does not fully mature.
Anisopoikilocytosis
Variance in size and shape of RBC.
Ovalocytes
Oval shaped RBC.
Hypersegmented neutrophils
6 or more lobes in nuclei rather than normal 2-5.