Haematological disorders

Flashcards by , created almost 6 years ago

(Biology of Disease) Flashcards on Haematological disorders, created by sophietevans on 07/29/2013.

Created by sophietevans almost 6 years ago
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Question Answer
What is anaemia? Anaemia is a reduction in the haemoglobin concentration in the blood resulting in a decreased ability to carry oxygen. It is a consequence one of a number of conditions underlying effective erythrocyte production or excessive loss of erythrocytes from the circulation.
What are the normal haemoglobin concentrations for an average adult male and female? <13.5 g/dL and <11.5 g/dL, respectively.
What are the normal haemoglobin concentrations for children between 2 years old and puberty, and foetuses? <11 g/dL and <14 g/dL, respectively.
What accompanies a reduction in haemoglobin? A fall in erythrocyte count.
List three causes of anaemia that results from problems with haemoglobin/erythrocyte production. Iron deficiency, vitamin B12 deficiency, and aplastic anaemia resulting from bone marrow hypoplasia (in turn resulting from thyroid, liver or renal disease, or from iatrogenic exposure to cytotoxic drugs, chemicals or radiotherapy).
What causes the aplastic anaemia resulting from bone marrow dysfunction? Reduced erythropoiesis as a result of the damaged tissue produces fewer erythrocytes and so there is less haemoglobin in the blood and a lower oxygen carrying ability.
What types of anaemia do iron deficiency and vitamin B12 deficiency cause, with regard to the erythrocytes? Iron deficiency causes microcytic anaemia, whereas vitamin B12 deficiency causes macrocytic anaemia.
What about iron deficiency results in microcytic anaemia or a reduced haemoglobin content within erythrocytes? The lack of iron results in diminished haem synthesis for erythropoiesis!
List some causes of iron deficiency that may result in iron deficient anaemia. Dietary lack (most common in vegetarians and vegans), increased demand (such as in pregnancy), or chronic blood loss (such as a stomach ulcer; iron is irretrievably lost and dietary sources cannot compensate).
What measurable characteristics are affected in iron deficiency anaemia (that could be checked in a blood test)? There is low serum iron, low serum ferritin, and raised serum transferrin (an increased capacity for transport).
Vitamin B12 deficiency results in macrocytic anaemia which are significantly reduced in number. What causes this? Vitamin B12 is necessary for the nuclear maturation, which lags behind that of the cytoplasm (a megaloblastic change) and results in the macrocytes as growth is not stopped after the usual period of time.
List some causes of vitamin B12 deficiency that results in macrocytic anaemia. Dietary lack (rare, but possible in vegetarians and vegans particularly), coeliac disease (malabsorption), malabsorption (e.g. lack of intrinsic factor produced by the parietal cells in the fundus of the stomach, or auto-antibodies to the parietal cells present), or metabolic interference (e.g. nitrous oxide anaesthesia leading to megaloblastic change).
Destruction of erythrocytes under how many days is classed as premature destruction? <120 days
In anaemia resulting from premature destruction of erythrocytes, the erythrocytes are abnormal. List some causes of abnormal erythrocytes. Haemoglobinopathies (e.g. sickle cell disease), thalassaemias, and haemolytic anaemia.
What is the substitution that results in sickle cell anaemia? It is a homozygous condition in which valine is substituted for glutamic acid at position 6 of the beta chain of haemoglobin A.
What is the abnormal shape of erythrocytes in sickle cell disease, what causes it and what effects does this have? Erythrocytes are sickle shaped, they precipitate into long filaments under low oxygen tension and these sickle-shaped cells get trapped in small blood vessels and cause painful infarctions as well as reducing the lifespan of the cell.
What are the thalassaemias? Conditions of a quantitative globin chain defect, resulting from an imbalance in the rate of synthesis of alpha- and beta-globin chains. This is caused by deletion or alteration of genes on chromosome 16 (for alpha-globins) and chromosome 11 (for beta-globins).
Which type of thalassaemia is less severe, compatible with life, and treatable? Beta-thalassaemia, which is treatable by blood transfusions and has a blood picture similar to iron deficiency anaemia and a clinical presentation of the classic anaemic symptoms.
Describe an auto-immune mechanism that causes haemolytic anaemia. If antibodies are produced against antigens existing on erythrocytes, the erythrocytes will be 'tagged' for premature removal from the circulation and destruction by macrophages and in the spleen. The bone marrow may not be able to increase erythropoiesis to fully compensate for the imbalance, resulting in anaemia.
How might a congenital structural difference in an individual's haemoglobin reduce their erythrocyte lifespan? The structure is less stable.
Describe how an erythrocyte's enzymes might result in anaemia. Structural defects of intracellular enzymes in erythrocytes may reduce their ability to metabolise efficiently and provide for their energy needs which reduces their lifespan.
How might a change in an erythrocyte's membrane structure result in anaemia? Erythrocyte membrane defects affect the biconcave discoid shape and reduce the ability to pass through small blood vessels. They are trapped in the splenic sinusoids and removed from the circulation prematurely, thus decreasing the erythrocyte number and the haemoglobin concentration of the blood - and it's oxygen-carrying capacity.
What is spherocytosis? Spherocytosis is an inherited defect which results in spherical erythrocytes with a reduced lifespan. An increased rate of erythropoiesis tends to compensate for this but if a person's health is compromised in some way, there may be periodic anaemia, or 'haemolytic crisis'.
What is the correct term for blood loss? Haemorrhage.
Describe acute haemorrhage. Acute haemorrhage usually results from trauma and the bone marrow can generally increase erythropoiesis to compensate for the blood loss within a couple of weeks, as long as bleeding does not continue.
Describe and give examples of chronic haemorrhage. Chronic haemorrhage is ongoing blood loss, as in heavy menstruation or an ulcer. In the early stages, the compensatory mechanisms are initiated but later this may not be possible due to the continued loss and dietary iron not being able to compensate. The result is invariably iron deficiency.
What are the general symptoms of anaemia? Fatigue, weakness, shortness of breath, cardiac failure in older patients, pale pallor of mucous membranes.
Describe a symptom specific to iron deficient anaemia. 'Spoon nails', in which the nails are dented.
Name a symptom specific to sickle cell anaemia. Leg ulcers.
What does it mean to say that a haematological malignancy is clonal? That the malignancy arose from a single cell that has undergone genetic mutation in cellular genes, sometimes arising from a single mutation but in some cases two mutations are required.
What is a myeloma? A non-leukaemia proliferative disorder in which there is malignant transformation of B cells. The B cells do not undergo apoptosis and instead survive and continue producing large amounts of antibodies.
What is a lymphoma? A non-leukaemia proliferative disorder in which a part of the lymphatic system has undergone malignant transformation.
What is polycythaemia? A non-leukaemia proliferative disorder in which too many erythrocytes are produced (erythropoiesis is overactive) and the blood becomes viscous and blood pressure is increased.
What does it mean to describe acute leukaemias as aggressive (in most cases)? That symptoms of the disease appear early.
Why are acute leukaemias rapidly fatal if left untreated? Acute leukaemias involve malignant transformations in early haemopoietic progenitors which means that they do not got on to form the different types of blood cells necessary for normal physiological function. The changes so early on result in the diseases being rapidly fatal if left untreated.
What is an acute leukaemia? An uncontrolled, clonal proliferation of immature, poorly differentiated cells (blasts).
What is acute lymphoblastic leukaemia (ALL)? Uncontrolled clonal proliferation of lymphoid progenitor proliferating cells.
What is acute myeloblastic leukaemia (AML)? Uncontrolled, clonal proliferation of myeloid progenitor proliferating cells.
What is common of both acute myeloid and acute lymphoid leukaemia? Both produce large numbers of abnormal leukocytes.
Without treatment, what is the life expectancy of an individual with acute leukaemia? Between weeks and months of developing the disease.
How do acute leukaemias cause morbidity and mortality? There is a deficiency in normal blood cell number or function, which can result in increased susceptibility to infection as well as slower recovery, and also in anaemia which lowers energy levels generally, as well as invasion of vital organs with the impairment of normal function.
Which type of leukaemias is most amenable to treatment? Acute leukaemias.
Chemotherapy causes morbidity by affecting all rapidly dividing cells. Give some examples of cell types that may be affected. Hair, endothelial intestinal cells, reproductive cells e.g. sperm.
Are all childhood leukaemias considered to be curable? Yes!
Without treatment, what is the life expectancy of an individual with a chronic leukaemia? It is measured in years.
What is the difference between chronic and acute leukaemia? Chronic leukaemias are caused by malignant transformation of blood cells later in their maturation than in acute leukaemia.
Why might the disease be monitored and care be palliative, rather than treated? Because the treatment may be more toxic than the disease in older patients.
Does conventional chemotherapy for chronic leukaemia increase survival time? Yes, but not significantly.
Roughly outline a bone marrow transplant. The haemopoietic system is removed, and completely eradicated with chemotherapy and radiotherapy, before being replaced with donor bone marrow from a person with a similar antigenic makeup to the recipient.
How does imatinib, the chemotherapeutic agent, work? Imatinib is a signal transduction inhibitor that works by blocking growth signals within the malignant cells which cause them to grow and divide. Imatinib minimises symptoms and is very effective, though it is a lifelong drug.
Why are sweating and weight loss common in all leukaemias? Because the basal metabolic rate is increased to support the rapid growth and division of the malignant cells.
List some typical features of all leukaemias. Anaemia, neutropenia (low neutrophil count), often leads to secondary infection and thrombocytopenia (low platelet count) due to bone marrow infiltration by leukaemic cells, infiltration of other organs and tissues by leukaemic cells.