30 Questions
What is the main characteristic of macrocytic anemia?
Abnormally large red blood cells
What is the significance of hypersegmented neutrophils in the diagnosis of megaloblastic anemias?
They are an important diagnostic feature of megaloblastic anemias
What distinguishes megaloblastic from non-megaloblastic (normoblastic) macrocytic anemias?
Appearance of developing erythroblasts in the bone marrow
What is the cause of macrocytic anemia?
Impaired DNA synthesis
What is the main characteristic that differentiates megaloblastic from non-megaloblastic macrocytic anemias?
Appearance of developing erythroblasts in the bone marrow
What is the significance of hypersegmented neutrophils in megaloblastic anemias?
They are an important diagnostic feature of megaloblastic anemias
What is the cause of pernicious anemia?
Defective secretion of intrinsic factor
Which enzyme is affected by the 677 C→T mutation in the MTHFR gene?
5,10 methylene tetrahydrofolate reductase
What is the main form of circulating B12 that is involved in the conversion of methylmalonyl CoA to succinyl CoA?
Deoxy-adenosyl-cobalamine
What is the result of folate or vitamin B12 deficiency in the mother during pregnancy?
Elevated homocysteine and S-adenosyl homocysteine in the fetus
What is the effect of the 5,10- methylene THF polyglutamate in cellular metabolism?
Essential for DNA synthesis
Why is monitoring and managing gastrin levels important for individuals with pernicious anemia?
To manage potential complications like gastric cancer
What is the main characteristic of macrocytic anemia?
Increased mean corpuscular volume (MCV)
Which condition can cause macrocytosis or hypersegmented neutrophils without megaloblastic anemia?
Liver disease
What are common causes of macrocytic anemia?
Alcoholism and liver disease
What is a characteristic feature of aplastic anemia?
Reduction in blood cell production in bone marrow
What are the main nutritional deficiencies associated with macrocytic anemia?
Folate and vitamin B12 deficiencies
What is the impact of chronic alcohol use on RBC production?
Suppresses bone marrow, affecting RBC production
What are the clinical features of megaloblastic anemia?
Jaundice, glossitis, and signs of anemia
What is the role of vitamin B12 in the body?
Conversion of methionine to S-adenosylmethionine for myelin synthesis
What are the hematological findings associated with folate deficiency?
Macrocytic anemia, anisocytosis, and hypersegmented neutrophils
What can cause vitamin B12 deficiency?
Lack of intrinsic factor secreted by gastric parietal cells
What is the treatment for folate deficiency?
Folic acid supplements and addressing the underlying cause
What are the causes of megaloblastic anemia?
Vitamin B12 or folate deficiency or antifolate drugs
What is the average daily intake of Folate in adults?
200-250 μg
Which vitamin has a dietary source that includes most foods, especially liver, green vegetables, and yeast?
Vitamin B12
What are the forms of Folate supplementation?
Dietary supplement, multivitamin
Which condition responds to uridine and is not related to Cobalamin or Folate deficiency?
Orotic aciduria
What are the causes of Vitamin B12 deficiency?
Malabsorption, Inadequate intake, Intrinsic factor deficiency, Long-term dialysis
What are the mechanisms of folate deficiency caused by anticonvulsant therapy?
Impaired absorption, Increased metabolism, Altered folate metabolism
Study Notes
- Megaloblastic Anemia can be caused by deficiencies or abnormalities of Cobalamin (B12) and Folate.
- Causes of Megaloblastic Anemia not related to Cobalamin or Folate deficiency: a. Some cases of acute myeloid leukaemia, myelodysplasia, b. Orotic aciduria (responds to uridine), c. Therapy with drugs interfering with synthesis of DNA (e.g. cytosine arabinoside, hydroxyurea, 6-mercaptopurine, azidothymidine (AZT)), d. Thiamine responsive.
- Other rare causes suggested but poorly documented: a. Vitamin E deficiency, b. Lesch-Nyhan syndrome (responds to adenine).
- Other causes of megaloblasts: a. Abnormalities of nucleic acid synthesis, b. Orotic aciduria, Drug therapy: 1-Antipurines (mercaptopurine,azathioprine), 2-Antipyrimidines (fluorouracil, zidovudine (AZT)), 3-Others (hydroxyurea).
- Myelodysplastic syndromes, erythroleukaemia, Some congenital dyserythropoietic anaemias, Uncertain aetiology.
- Vitamin B12 & Folate:
- Dietary source: Vitamin B12: Only food of animal origin, especially liver. Folate: Most foods, especially liver, green vegetable and yeast.
- Average daily intake: In adults: Vitamin B12: 7-30 μg, Folate: 200-250 μg.
- Body stores: Vitamin B12: 3-5 mg, mainly in the liver. Folate: 8-20 mg, mainly in the liver.
- Time to develop deficiency: Anemia in 2-10 years, Macrocytosis in 5 months.
- Structure: Vitamin B12: Methylcobalamin, Adenosylcobalamin, Hydroxocobalamin, Cyanocobalamin. Folate: Tetrahydrofolic acid (THF), Methyl THF.
- Forms: Vitamin B12: Injection, oral tablet, nasal spray, liquid. Folate: Dietary supplement, multivitamin.
- Causes of Vitamin B12 & Folate deficiency: Vitamin B12 deficiency: Malabsorption, Inadequate intake, Intrinsic factor deficiency, Long-term dialysis, Congenital intrinsic factor deficiency. Folate deficiency: Malabsorption, Inadequate intake, Increased requirement, Anticonvulsant therapy, Ethanol abuse, Certain anticonvulsant medications, Pregnancy, Premature infants, Chronic haemolytic anaemias, Myelofibrosis, Various malignant diseases, Increased loss.
- Mechanisms of folate deficiency caused by anticonvulsant therapy: 1. Impaired absorption, 2. Increased metabolism, 3. Altered folate metabolism.
- Manifestations of Vitamin B12 & Folate deficiency: Neurological: Megaloblastic anemia, Severe Megaloblastic anemia, Neuropathy, Neuropathy due to Vit B12 and folate deficiency. Hematological: Neural tube defect. Psychiatric symptoms.
Test your knowledge about the causes of megaloblastic anemia including B12 and folate deficiencies, therapy-related causes, and independent factors. Discover the various factors that contribute to this type of anemia.
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