Macrocytic Anaemia Flashcards
What is Macrocytic Anaemia?
Diagnosed when MCV > 96fL
What are the 2 main types of Macrocytic Anaemia?
- Megaloblastic
- Normoblastic
What is meant by the term Megaloblastic?
Refers to the presence of abnormally large, immature red blood cells
What are the Megaloblastic causes of Macrocytic Anaemia?
- Vitamin B12 deficiency
- Folate deficiency
- Drugs that interfere with B12/folate metabolism
What are the Normoblastic causes of Macrocytic Anaemia?
- Alcohol
- Liver Disease
- Hypothyroidism
- Pregnancy
- Reticulocytosis (increased number of reticulocytes)
- Myelodysplasia
What are the different causes of Folate Deficiency?
=> Increased demand
- Pregnancy/breast feeding
- Infancy and growth spurts
- Haemolysis and rapid cell turnover
- Disseminated cancer
- Urinary losses
=> Decreased intake:
- Poor diet
- Elderly
- Chronic alcohol intake
=> Decreased absorption:
- Medication
- Coeliac disease
- Jejunal resection
- Tropical Sprue
What is the main problem is a deficiency in maternal folate in fetuses?
Neural tube defect
=> Prophylactic doses of folate to at least 12 weeks gestation prevents development of spina bifida
What is the role of Vitamin B12?
Essential co-factor in the methylation of DNA and cell metabolism
What molecule is required for the absorption of Vitamin B12?
=> Absorption occurs in the terminal ileum?
- Intrinsic Factor needed
Where is Intrinsic Factor produced?
Parietal cells of stomach
What 2 glycoproteins are responsible for the transport of vitamin B12 to tissues?
- Transcobalamin I
- Transcobalamin II
What are the causes of Vitamin B12 deficiency?
=> Impaired absorption
- Pernicious Anaemia
- Gastrectomy or ileal resection
- Zollinger-Elission syndrome
- Parasites
=> Decreased intake
- Malnutrition
- Vegan diet
=> Congenital causes
- Intrinsic Factor receptor deficiency
- Cobalamin mutation
=> Increased requirements
- Haemolysis
- HIV
- Pregnancy
- Growth spurts
=> Medication
- Alcohol
- NO
- PPI
- H2 antagonists
- Metformin
What is the clinical presentation of Vitamin B12 deficiency?
BRAIN => Cognition, Depression, Psychosis
NEUROLOGY => Myelopathy, Sensory changes, Ataxia, Spasticity
TONGUE => Glossitis, Taste impairment
BLOOD => Pancytopenia
- Infertility
- Cardiomyopathy
What are the investigations in suspected Macrocytic Anaemia?
=> Blood films
Hypersegmented Neutrophils
=> Bone Marrow Biopsy - may show:
- Megaloblastic bone marrow
- Normoblastic bone marrow
- Abnormal erythropoiesis
- Increased erythropoiesis
What is the management of Macrocytic Anaemia?
- Folic Acid 5mg/day PO for 4 months
- Give Vitamin B12 in all cases UNLESS SPECIFICALLY PROVEN THE PATIENT IS NOT VITAMIN B12 DEFICIENT
=> If no neurological involvement 1 mg of IM hydroxocobalamin 3 times each week for 2 weeks, then once every 3 months
