<prompt> Macrocytic anaemia in children is produced by all exceptThiamine deficiencyOrotic acideueiaCopper deficiencyLiver disease  <response>: Morphology of RBC Normal human red blood cells are biconcave discs diskocytes with a mean diameter of about 7.5 m.The hemoglobin of red cells is located peripherally, leaving an area of central pallor equal to approximately 30-35 of the diameter of the cells. Cells of normal size and normal hemoglobin content color are termed normocytic and normochromic.When red cells diameter is greater than 9 mm, they are referred to as macrocytes.When red cells diameter is less than 6 mm, they are referred to as microcytes.Variation in size of RBCs is known as anisocytosis.Variation in shape of RBCs is known as poikilocytosis.Causes of macrocytosisCauses of megaloblastic anemia :Vitamin B12 deficiency : Decrease intake - Inadequate diet, vegetarianism.Impaired absorption :Intrinsic factor deficiencyPernicious anaemiaGastrectomyMalabsorption statesDiffuse intestinal disease eg Lymphoma, systemic sclerosis.Beal resection, ilitisCompetitive parasitic uptake eg. fish tape worm infestation.Bacterial over growth in blind loops and diverticula of bowel.Increased requirement: pregnancy, hyperthyroidism, disseminated cancer.Folic acid deficiency :Decreased intake : inadequate diet, alcoholism infancyImpaired absorption e.g. malabsorption stateIntestinal diseasesAnticonvulsants, OCP.Increased loss: haemodialysisIncreased requirement : Pregnancy, infancy, disseminated cancer markedly increased haemoptysis.Impaired use : folic acid antagonist.Other causes of megaloblastic anemiaThiamine deficiency Pyridoxine deficiency Hereditary orotic aciduria Congenital dyserythropoietic anemia Di-Gueglielrno syndrome Hypothyroidism 