Haematology

• Blood is composed of plasma, which contains red blood cells, white blood cells, platelets and clotting factors such as fibrinogen.
• Once the clotting factors are removed from the blood, what is left is called the serum.
• Serum contains glucose, electrolytes such as sodium and potassium, and proteins such as immunoglobulins (antibodies) and hormones.
• Blood cells develop in the bone marrow, which is mostly found in the pelvis, vertebrae, ribs and sternum.
• Pluripotent haematopoietic stem cells are undifferentiated cells that can transform into various blood cells.
• These cells initially become myeloid stem cells and lymphoid stem cells.
• Red blood cells develop from reticulocytes, which originate from myeloid stem cells.
• Reticulocytes are immature red blood cells that survive around four months (120 days).
• Platelets are made by megakaryocytes, which develop from the myeloid stem cells.
• The lifespan of platelets is around ten days.
• The normal count is 150 – 450 x 10^9/L.
• The role of platelets is to clump together (platelet aggregation) and plug gaps where blood clots need to form.
• Anaemia is defined as a low concentration of haemoglobin in the blood, which is the consequence of an underlying disease, not a disease itself.
• An- means without, and -aemia refers to blood.
• Haemoglobin is a protein found in red blood cells.
• White blood cells originate from myeloid stem cells and become myeloblasts, which can become monocytes, then macrophages, neutrophils, eosinophils, mast cells, basophils, and lymphocytes.
• Lymphocytes come from the lymphoid stem cells and become B cells or T cells.
• Haemoglobin is responsible for picking up oxygen in the lungs and transporting it to the body’s cells.
• Iron is essential in creating haemoglobin and forms part of its structure.
• The mean cell volume (MCV) refers to the size of the red blood cells and is highly relevant in anaemic patients.
• Haemoglobin: 120 – 165 grams/litre
• Mean Cell Volume (MCV): 80-100 femtolitres
• Anaemia is divided into three categories based on the mean cell volume: Microcytic anaemia (low MCV), Normocytic anaemia (normal MCV), and Macrocytic anaemia (large MCV).
• Iron is an important part of the haemoglobin molecule.
• Iron deficiency leads to anaemia, a low concentration of haemoglobin.
• The mnemonic for remembering the causes of microcytic anaemia is “TAILS”: T stands for thalassaemia, A for anaemia of chronic disease, I for iron deficiency anaemia, L for lead poisoning, and S for sideroblastic anaemia.
• Iron deficiency causes microcytic hypochromic anaemia, where the red blood cells are small and pale due to a reduced haemoglobin concentration.
• Anaemia of chronic disease often occurs with chronic kidney disease due to reduced production of erythropoietin by the kidneys, the hormone responsible for stimulating red blood cell production.
• Treatment for anaemia of chronic disease is with erythropoietin.
• Several scenarios can lead to iron deficiency, including insufficient dietary iron, reduced iron absorption, increased iron requirements, loss of iron through bleeding, and blood loss.
• Smudge cells are ruptured white blood cells that occur while preparing the blood film when the cells are aged or fragile, particularly associated with chronic lymphocytic leukaemia.
• B lymphocytes ( B cells ) mature in the bone marrow and differentiate into: Plasma cells, Memory B cells, T lymphocytes ( T cells ) mature in the thymus gland and differentiate into: CD4 cells (T helper cells), CD8 cells (cytotoxic T cells), Natural killer cells.
• Anisocytosis refers to a variation in the size of the red blood cells, which can be seen in myelodysplastic syndrome and many types of anaemia, such as iron deficiency, pernicious and autoimmune haemolytic anaemia.
• Sideroblasts are immature red blood cells with a nucleus surrounded by iron blobs, indicating sideroblastic anaemia, which occurs when the bone marrow cannot incorporate iron into the haemoglobin molecules due to either a genetic defect or myelodysplastic syndrome.
• A blood film involves the manual examination of the blood using a microscope, looking for abnormal shapes, sizes and inclusions (contents) of the cells.
• Schistocytes are fragments of red blood cells, indicating that red blood cells are being physically damaged during their journey through the circulation, seen in microangiopathic haemolytic anaemia (MAHA), which occurs when small blood clots (thrombi) obstruct small blood vessels, causing haemolysis (rupture), key causes of MAHA are haemolytic uraemic syndrome (HUS), disseminated intravascular coagulation (DIC) and thrombotic thrombocytopenic purpura (TTP), Schistocytes can also be seen in metallic heart valve replacement as the metallic valves damage the red blood cells.
• Howell-Jolly bodies are individual blobs of DNA material seen inside red blood cells, which the spleen would normally remove, seen in patients after a splenectomy or with a non-functioning spleen, such as caused by sickle cell anaemia, and also seen in severe anaemia, where the body is regenerating red blood cells very fast.
• Target cells are red blood cells with a central pigmented area surrounded by a pale area, surrounded by a ring of thicker cytoplasm on the outside, mostly seen in iron deficiency anaemia and post-splenectomy.
• Heinz bodies are individual blobs ( inclusions ) seen inside red blood cells, which are denatured (damaged) haemoglobin, mostly seen in G6PD deficiency and alpha-thalassaemia.
• Spherocytes are sphere-shaped red blood cells without the bi-concave disk shape, indicating autoimmune haemolytic anaemia or hereditary spherocytosis.