Red Cells Flashcards
Definition of anaemia
The reduction in red cells or their haemoglobin content
Hb below normal for age and sex
Causes of anaemia
Blood loss
Increased destruction
Lack of production
Defective production
If the bone marrow is stressed, what will it do?
Tip out more reticulocytes
What is the cell before the cell turns into a erythrocyte?
Reticulocyte
Developmental pathway of a RBC
- Ribosome synthesis
- early erythroblast - haemoglobin accumulation
- late erythroblast to normoblast - ejection of nucelus
- reticulocyte
Substances required for RBC production
Metals - iron - copper - cobalt - manganese Vitamins - B12 - Folic acid - thiamine - Vit B6 - Vit C - Vit E Amino acids Hormones - erythropoietin (produced by the liver) - GM-CSF - Androgens - thyroxine - SCF
Where does RBC breakdown occur and how?
reticuloendothelial system by macrophages
Globin - amino acids reutilised
Haem - iron reutilised and haem broken down to biliverdin and eventually to bilirubin
where are macrophages found that remove RBCs?
Spleen
Lymph nodes
Lungs
Where are the majority of RBCs removed?
Spleen
How is bilirubin transferred?
By haem - bound to the albumin in the plasma
Another name for a mature RBC
Erythrocyte
How long do RBCs last for?
120 days
Features of a RBC
Biconcave disc shape Membranes enzymes haemoglobin deformable - can squeeze through the vasculature and allows them to last longer in the circulation
Congenital anaemias are caused by 1 of 3 causative features
- in red cell membrane
- in red cell metabolic pathways (enzymes)
- In haemoglobin synthesis
Possible defect in the red cell membrane causing anaemia
Defects in skeletal proteins in the lipid bilayer can lead to increased abnormal cells leading to increased haemolysis and increased destruction
What skeletal proteins can have defects?
Ankyrin
Spectrum
Band 3
Pathology of hereditary spherocytosis
defects in 5 different structural proteins - ankyrin - alpha spectrin - beta spectrin - band 3 - protein 4.2 Red cells are spherical Removed by the RE system (extravascular) as the spleen recognises them as the wrong shape
Presentation of hereditary spherocytosis
Variable anaemia jaundice (neonatal) Splenomegaly - due to the spleen working overtime Pigment gallstones (deposits of excess bilirubin)
Why does hereditary spherocytosis result in jaundice?
Break down a red cell faster than normal -> bilirubin will rise -> jaundice (prolonged)
Treatment of hereditary spherocytosis
Folic acid (increased requirements) Transfusion (if intermittent illness e.g. virus/drugs/unwell as this causes increased haemolysis) Splenectomy (due to chronic haemolysis as the spleen is destroying all the RBCs)
Two pathways of red cell enzymes
Glycolysis - provides energy
Pentose phosphate shunt - protects from oxidative damage
Two key enzymes that you can get congenital deficiencies of
2,3-DPG
Pyruvate kinase
What does Glucose 6 phosphate dehydrogenase (G6PD) do?
Neutralises free radicals which are highly reactive.
Pathology of G6PD deficiency
Red cells become very prone to free radical injury resulting in intravascular haemolysis
What does G6PD deficiency confer a protection against?
Malaria
Genetics of G6PD deficiency
X linked
- Affects males
- Female carriers
Features of cells in G6PD deficiency
Blister cells
Bite cells
Heinz bodies
Presentation of G6PD Deficiency
neonatal jaundice Drug, broad bean or infection precipitated jaundice and anaemia - intravascular haemolysis - haemoglobinuria Splenomegaly Pigment gallstones
Triggers for haemolysis in G6PD Deficiency
Infection acute/intercurrent illness e.g. DKA Broad (fava) beans drugs - antimalarials - sulphonamides and sulphones - antibacterials (nitrofunantoin) - analgesics (big doses of aspirin) - antihelminthes - vit K analogues - methylene blue
Pathology of pyruvate kinase deficiency
Reduced ATP - leading to blockage
Increased 2,3-DPG - leading to rigid cells
Cells being rigid means that they are more liable to haemolysis in the circulation
Presentation of pyruvate kinase deficiency
Anaemia
Jaundice
Gallstones
How common is pyruvate kinase deficiency?
Rare
Function of haemoglobin
Oxygen binding and unloading
- gives up O2 more readily when you need it e.g. exercise
- vasodilation in e.g. exercise when warm - give up O2 more easily
Gas exchange
- O2 to tissues
- CO2 to lungs
Features of the “Bohr effect”
Acidosis
Hyperthermia
Hypercapnia
Fetal haemoglobin vs adult haemoglobin
Foetal haemoglobin has a higher affinity than adult haemoglobin for O2
What is haemoglobin made up of?
A haem molecule 2 alpha chains 4 alpha genes (Chr16) 2 beta (B) chains 2 beta genes (Chr 11)
Two types of adult haemoglobin
Hb A (aaBB) - 97% Hb A2 (aadd) - 2%
Genes of foetal haemoglobin
aagg - 1%
What happens if all alpha genes are lost in terms of haemoglobin?
Incompatible with life as any combination made requires alpha genes however if other genes were missing e.g. beta chains then other genes can take over e.g. delta
What are haemoglobinopathies?
Inherited abnormalities of haemoglobin synthesis
Pathologies of haemoglobinopathies, either…
Reduced or absent globin chain production - thalassaemia
or
mutations leading to structurally abnormal globin chain - HbS, HbC, HbD etc
What does HbSS mean/present with?
Sickle cell disease
What is sickle cell disease haemoglobin composed of?
A haem molecule
2 a chains
2 b (sickle) chains
Pathology of sickle cell disease
HbS under conditions of stress e.g. hypoxia
- the Hb crystallises and forms a rigid structure and so then the red blood cell changes shape - SICKLES (this is irreversible). (NOT A DEFECT OF CELL MEMBRANE)
even when trying to carry oxygen again it stays in this sickle shape
This leading to
Red cell injury, cation loss, dehydration (due to leaking)
- HAEMOLYSIS
- chronic lifelong vasculopathy (major risk factor for stroke)
endothelial activation
promotion of inflammation
Vaso occlusion - impaired passage of the RBC clogs vessels and tissue infarcts
Diagnosis of sickle cell disease
Blood film
Presentation of sickle cell disease
Painful vasoocclusive arteries - bone - very severe - often requiring very opiates in hospital Chest crisis - hypoxia - chest pain - fever - infiltrates on X ray Stroke / mental retardation Increased infection risk (hyposplenism) chronic haemolytic anaemia sequestrian crisis Hepatomegaly Auditory impairment Retinopathy Cardiomegaly -> CHF Bone marrow hyperplasia Aseptic bone necrosis - > osteomyelitis infarcts of extremities vaso occlusion ulcer Delayed puberty Reduced fertility Obstetric complications Immunosuppression Bony deformity (physical disability) Priapism (involuntary erection of penis) splenomegaly pulmonary infarcts -> pneumonia Renal pathology Growth impairment (endocrine dysfunction)
Treatment of chest crisis of sickle cell disease
Resp support Antibiotics IV fluids TRANSFUSION to give HbA - to keep HbS < 30% so more like a carrier state
Prognosis of sickle cell disease
life expectancies
- men 42 y/o
- women 48 y/o
perinatal and childhood morality associated with this
treatment of sickle cell disease
Avoid precipitants life long prophylaxis - vaccination - penicillin (and malarial) prophylaxis - folic acid acute events - hydration - oxygenation - prompt treatment on infection - analgesia (NSAIDs, opiates) Blood transfusion if severe anaemia Exchange transfusions to reduce HbS < 30% Disease modifying drugs (hydroxycarbamide) Bone marrow transplantation Gene therapy
Definition of thalassaemia’s
Reduced or absent globin chain production
Pathology of thalassaemias
Mutations or deletions in
- alpha genes (alpha thalassaemia)
- beta genes (beta thalassaemia)
Chain imbalance due to deleted genes leading to chronic haemolysis and anaemia
Types of thalassaemia’s
Homozygous alpha zero thalassaemia
Beta thalassaemia major (homozygous beta thalassaemia)
Non-transfusion dependent thalassaemia (intermedia)
Thalassemia minor
Features of homozygous alpha zero thalassaemia
No alpha chains - 4 genes affected
Hydrops fetalis - incompatible with life
Death occurs in utero
Features of beta thalassaemia major (homozygous beta thalassaemia)
No beta chains
Hugely metabolic active condition
Transfusion dependent anaemia but will survive
Presentation of beta thalassaemia major
Severe anaemia - presenting at 3-6 months of age - expansion of maxillary sinuses and mandible - expansion of ineffective bone marrow - bony deformities - splenomegaly - growth retardation - hair on end appearance of skull on X ray Failure to thrive
Treatment of beta thalassaemia major
Chronic transfusion support - 4-6 weekly Iron chelation - S/C deferoxamine infusions - oral deferasirox Bone marrow transplantation (curative)
What does iron chelation do?
Takes away the excess iron
Why does beta thalassaemia major not show any symptoms until 3-6 months of life?
After the foetal haemoglobin goes down and the adult haemoglobin fails to rise do you get symptoms and therefore need a transfusion
Life expectancy of beta thalassaemia major
untreated or with irregular transfusions < 10 y/o
normal life expectancy (>40 y/o) following blood transfusion and iron removal
Features of thalassaemia minor
“trait” or carrier state
Hypochromic microcytic red cell indices - small red cells
only really significant if partner has it as well as it may affect baby
Presentation of thalassaemia minor
Very mild anaemia sometimes but usually absaloutly fine
mostly asymptomatic
Most common thalassaemia
Thalassaemia minor
Pathology of Haem synthesis defects
RARE
defects in mitochondrial step of haem synthesis result in SIDEROBLAST ANAEMIA
- ALA synthase mutations
- hereditary X linked
- acquired - myelodysplasia
Defects in cytoplasmic steps result in prophyrias
Normal range of Hb for male 12-70 y/o
140-180
Normal range of Hb for male > 70 y/o
116-156
Normal range of Hb for females 12-70 y/o
120-160
Normal range of Hb for females > 70 y/o
108-143
Factors influencing normal range of haemoglobin
Age
- babies born, within 48 hours are polycythemic and then at 4-6 weeks become anaemic
Sex (M > F due to testosterone)
ethnic origin
time of day sample taken - fasting sample = higher Hb
Time to analysis
= sitting in a tube will affect size and shape of cells
Presentation of acquired anaemias
Tiredness Palor Breathlessness Yellowing of eyes Swelling of ankles Dizziness chest pain Palpitations Angina Changed stool colour Muscular weakness Sore red tongue Kolinichia symptoms related to underlying cause - evidence of bleeding (menorrhagia, dyspepsia, PR bleeding) - malabsorption (diarrhoea, weight loss) - jaundice (due to haemolysis) - splenomegaly/lymphadenopathy (can show in both congenital and acquired)
Pathology of acquired anaemia - due to either….
Bone marrow - cellularity - stroma - nutrients Red cell - membrane - haemoglobin - enzymes Destruction loss - blood loss - haemolysis - hypersplenism
What do red cell indices do?
Automated measurement of red cell size and haemoglobin content
Red cell indices include
MCV
MCH
What does MCV mean?
Mean cell volume
What does MCH mean?
Mean cell haemoglobin
- how much haemoglobin is in each cell
Morphological types of anaemia
Hypochromic microcytic
Normochromic normocytic
Macrocytic
What morphological type of anaemia is the commonest worldwide?
Hypochromic microcytic
Features of hypochromic microcytic anaemia
Small and pale
Area of central palor with haemoglobin around the edges
Causes of hypochromic microcytic anaemia
Iron deficiency
Chronic bleeding
Thalassaemias
Chronic disease
Investigations of hypochromic microcytic anaemia
Serum ferritin
Interpretations of serum ferritin
if low = iron deficiency if normal or increased - thalassaemia - secondary anaemia - sideroblastic anaemia
What is secondary anaemia also known as?
Anaemia of chronic disease
Features of normochromic normocytic anaemia
looks like normal cells but there is less of them
big cohort of people will be in this
Investigations of normochromic normocytic anaemia
Reticulocyte count
Interpretation of reticulocyte count
If increased
- bone marrow working well and throwing out reticulocytes to try and compensate so e.g. Acute blood loss, haemolysis
If decreased
- bone marrow not working so e.g. secondary anaemia, hypoplasia, marrow infiltration
Causes of macrocytic anaemia
B12 deficiency folate deficiency underlying bone marrow problem alcohol drugs (methotrexate, ARVs, hydroycarbamide) Disordered liver function hypothyroidism myelodysplasia
Types of macrocytic anaemia
Megaloblastic
Non-megaloblastic