Failure of red cell production Dr Dupe Elebute Consultant Haematologist

Aim To revise the process and control of normal erythropoiesis To discuss the mechanisms of failure of red cell production

Overview Origin and control of red cell production Role of iron in haemoglobin structure and function Role of vitamin B12 and folic acid in red cell production Other causes of failure of red cell production

Erythropoiesis Erythropoiesis is the process of red blood cell production Erythrocytes are derived from the division and differentiation of a common stem cell precursor

Erythropoiesis: earliest stages BFU-E (day 3), CFU-E (day 7), immature erythroblast (day 11) and mature erythroblast (day 15). Romanowsky stain.

Erythropoietin Haemopoietic growth factor Main control of rbc production Produced in the kidney Released by low O2 tension (hypoxia, anaemia) Reacts with Epo receptors on red cell precursors to increase rbc production Recombinant Epo available (anaemia due to renal failure)

Haematinics Dietary substances Essential for production of red blood cells and Hb Most important: Iron Vitamin B12 Folic acid

Anaemia Reduced haemoglobin level Normal range depends on age and gender Subclassified by red cell indices Microcytic, hypochromic Normocytic, normochromic Macrocytic

Microcytic, hypochromic anaemia Definition: Caused by defective synthesis of Hb, resulting in red cells that are smaller than normal (microcytic) and contain reduced amounts of haemoglobin (hypochromic). Differential diagnosis: Iron deficiency anaemia Thalassaemia Sideroblastic anaemia

Iron Function Dietary source Major role in several metabolic processes Combines with protoporphyrin ring to form haem Four haem groups to each tetramer of Hb 1g of Hb can combine with 1.34ml of O2 Dietary source Present in food as ferric hydroxide Red meat best source

Iron Daily dietary iron requirements per 24 hours: Male 1 mg Adolescence 2-3 mg Female (reproductive age) Pregnancy 3-4 mg Infancy Maximum bioavailability from normal diet about 4 mg

Iron Absorption Transport Occurs in duodenum and jejunum Enhanced by acid and reducing agents 1-2mg (5-10%) absorbed daily Transport In plasma combined with transferrin Combined with apoferritin in RES Stored as ferritin

Iron deficiency anaemia (IDA) inadequate intake of iron dietary deficiency Malabsorption increased loss of iron menorrhagia gastro-intestinal bleeding haematuria increased need for iron Pregnancy and lactation Barium meal showing hiatus hernia causing IDA

IDA: signs and symptoms Rapidly progressive anaemia usually causes more symptoms Some people with severe anaemia have no symptoms at all Common symptoms of anaemia include: Tiredness; Fatigue Pale appearance Irritability; Headache Reduced exercise capacity Palpitations

IDA: signs and symptoms (2) Severe and prolonged deficiency may produce the following symptoms: Painless glossitis (tongue smooth and red) Curling and softening of the nails (spooning; koilonychia) Brittle hair Pica ( unusual dietary cravings) Nail changes in iron deficiency anaemia (koilonychia)

IDA: diagnosis Blood tests (FBC): Low Hb, MCV and MCH Blood film: the red blood cells are smaller (microcytic) than usual and paler in colour (hypochromic). Some of the red cells may have an abnormal shape (poikilocytosis; pencil cells) Platelet count may be raised

Normal blood film Hypochromic, microcytic picture with marked anisocytosis and poikilocytosis

IDA: diagnosis (2) Iron studies Serum iron: low (10-30μmol/l) Total iron binding capacity: high (50-70μmol/l) Transferrin saturation: low (>16%) Serum Ferritin level: low (12-150μg/l) best indicator of body iron status; when <12μg/l, indicates iron deficiency!

Iron stores in the bone marrow: The marrow smear is treated with potassium ferricyanide (Prussian blue) which stains the iron within the reticulo-endothelial cells blue. Reduced iron stores Normal iron stores

Differential diagnosis of a hypochromic anaemia IDA Anaemia of chronic disorder Thalassaemia trait Sideroblastic anaemia MCV, MCH, MCHC All  in relation to anaemia Low normal or mild reduction Very low for degree of anaemia  congenital  Acquired Serum iron  N  TIBC Serum ferritin N/ BM iron stores Absent Present

IDA:further investigations Dietary history Drug history: Aspirin, other anti-inflammatory Menstrual history Exclude GI tract malignancy faecal occult blood (checks faeces for microscopic amounts of blood) colonoscopy (tube test to look at the large bowel); gastroscopy. (tube test to look at gullet and stomach).

IDA: treatment Treat underlying cause Oral iron: Ferrous sulphate (67mg per 200mg tablet) Cheap! Treat for up 4-6 months to correct anaemia and replenish stores Hb rise of about 2g/dl every 3 weeks S/E include nausea, diarrhoea, constipation Reduce dose or use preparation with lower iron content .e.g. Ferrous gluconate (37mg per 300mg tablet Ferrous succinate, lactate, fumarate: more expensive

IDA: treatment Parenteral iron rarely used as allergic reactions, anaphylaxis quite common Preparations of iron dextran or iron-sorbitol-citrate given intramuscularly (I.M) or intravenously (I.V) Iron dextran can be given I.V in total dose infusion NB: Blood transfusion is rarely indicated and may be dangerous

Macrocytic anaemia Definition: Rise in the mean cell volume of the red cells above the normal range (adults 80-95 fl) Differential diagnosis: Reticulocytosis (acute bleeding) Vitamin B12 or folate deficiency Alcoholic liver disease Hypothyroidism Myelodysplasia (MDS)

Macrocytic anaemia: investigation Clinical Dietary history GI symptoms Alcohol consumption Hypothyroidism (lethargy, weight gain)

Macrocytic anaemia: investigation Blood film Hypersegmented neutrophils (B12 def) Target cells, stomatocytes (liver disease) Abnormal morphology (MDS)

Blood film in vitamin B12 deficiency showing macrocytic red cells and a hypersegmented neutrophil. Normal blood film

Macrocytic anaemia: investigation Reticulocyte count Liver and thyroid function tests Serum B12 and folate assays Bone marrow aspirate Megaloblastic features Alternative diagnosis (MDS, AA)

High power view of a normal bone marrow aspirate Megaloblastic features in BMA Megaloblastic BM: giant metamyelocytes

Vitamin B12 Source: Absorption: Only produced by micro-organisms Mainly from animal produce Stable to cooking Absorption: Mainly through the ileum Combines with intrinsic factor (IF) IF produced by gastric parietal cells Complex combines with IF receptors in terminal ileum ―› B12 absorbed

Vitamin B12 deficiency Minimum daily requirement: 1-2μg Body stores: 2-3mg (lasts for 2-4 yrs) Deficiency caused by: Malabsorption Dietary lack (vegans) Pernicious anaemia (antibodies directed against IF) Blind-loop syndrome

Vitamin B12 deficiency (2) Symptoms and signs: Macrocytic, megaloblastic anaemia Neurological symptoms – subacute combined degeneration of the cord Glossitis due to Vitamin B12 deficiency

B12 deficiency: investigation Radioactive vitamin B12 absorption with and without intrinsic factor (Schilling test) Serum gastric parietal and intrinsic factor antibodies Endoscopy–gastric biopsy (vitamin B12 deficiency), duodenal biopsy (folate deficiency)

B12 deficiency: treatment Hydroxycobalamin: parenteral preparation only Initial/loading dose of 1mg every 3-4 days for up to 6 doses Maintenance dose of 1mg every 3 months

Folic Acid Source: Most foods esp meat (liver), vegetables, yeasts Natural folates largely in the polyglutamate form Easily destroyed by cooking Absorption: Polyglutamates deconjugated and converted to monoglutamate 5-methyltetrahydrofolate Absorbed through duodenum and jejunum

Folic Acid Normal dietary intake 600-1000g Daily requirement 100-200g Body stores 10-12mg (enough for 4 months) Deficiency caused by: Inadequate dietary intake (lack of fresh veg!) Malabsorption: coeliac disease, tropical sprue Increased demands: pregnancy, proliferative disorders e.g. chronic haemolytic anaemia

Folate deficiency Symptoms and signs: Megaloblastic anaemia Neural tube defects in fetus No clear relation between maternal folate levels and defects but… Folic acid supplements in early pregnancy shown to reduce incidence of spina bifida, anencephaly, cleft palate and hare lip

Folate deficiency Treatment: B12 deficiency must be excluded first to prevent development/exacerbation of neurological disease Oral folic acid: 5mg daily Prophylaxis in pregnancy: 400g from time of conception

Bone marrow failure syndromes Acquired/Idiopathic Aplastic anaemia Red cell aplasia Acquired/Infection Parvovirus B19 Congenital Fanconi anaemia Diamond Blackfan anaemia

Bone marrow trephine biopsy showing normal ratio of haemopoietic cells and fat spaces Hypoplastic bone marrow Aplastic bone marrow

More Information from: Essential Haematology: Hoffbrand & Pettit Lecture notes on Haematology: Hughes-Jones & Wickramasingh ABC of clinical haematology: Provan