Megaloblastic Anemia Flashcards
What are the causes of megaloblastic anemia❓
Vitamin B12 deficiency
Vitamin B9 deficiency
Combined deficiency of B12 and B9
Drugs
Inherited metabolic diseases
How would you define megaloblastic anemia❓
A disorder characterized by:
- Defective nuclear maturation
- Due to impaired DNA synthesis
- Usually as a result of B12/B9 deficiency
What % of macrocytic anaemias is caused by B9 and or B12 deficiencies❓
30-50%
What MCV of RBC would pass for a macrocytic cell❓
MCV >95-100
What is the RDA of B12 for adults❓
What is the RDA of B12 for pregnant/lactating women ❓
A: 2 microgram/day
P: >2 microgram/day
L: 2.5-3 microgram/day
Average diet contains ____ B12/day
What is the plasma level of B12❓
5-30 microgram/day
200-900 ng/L
Amount of B12 stored up in the body is ❓
As❓
Where❓
How long would it take to deplete the store❓
2-5 mg
Adenosylcobalamin (coenzyme B12)
Liver
3-6 years
What is the plasma level of folate❓
_____ serum folate levels will qualify for folate deficiency
6-21 microgram/L
<4 microgram/L
The RDA of folate is❓
Diet contains how much folate per day❓
3 microgram/kg for >10yrs old
100-500 microgram/day
What is the RBC level of folate❓
_____ RBC folate levels will qualify for folate deficiency
160-640 microgram/L
<140 microgram/L
Amount of B9 stored up in the body is ❓
As❓
Where❓
5-20 mg
N5-methyl folate
Liver
Megaloblastic haematopoiesis presents with:
Anemia
+/-Leukopaenia
+/-Thrombocytopenia
Why❓
DNA synthesis is impaired and will affect all cell lines
What are the causes of VitB12 deficiency❓
⬇️intake:
Strict vegetarianism
🚫absorption:
Gastrectomy
Caustic injury
Ileal resection/disease
Pancreatic insufficiency
Imerslund-Grasbeck dx (familial selective B12 absorption defect
Drugs (colchicin, neomycin, omeprazol, ethanol)
Causes of folate deficiency❓
⬇️intake:
Alcoholism
Tropical/non-tropical sprue
Intestinal resection
⬆️demands: Pregnancy Chronic hemolytic dx Myeloproliferative dx Dermatitis Hyperthyroidism
Drugs: Oral contraceptives Anticonvulsants Triamtrene Cholestyramine
What are the causes of combined deficiency of B9 and B12❓
Tropical sprue
Gluten enteropathy
What could cause acute megaloblastic anemia❓
NO anesthesia
Dialysis
Drugs like trimethoprim
Parenteral feeding
Megaloblastic anemia can be due to what drugs❓
DHFR inhibitors eg methotrexate
Trimethoprim
Purine antagonists eg
Azathioprin
Pyrimidine antagonists eg
ARA-C
Alkylators eg
Cyclophosphamide
Zidovudine
Which inherited metabolic disorders could lead to megaloblastic anemia❓
Orotic aciduria
Lesch-Nyhan Syndrome
Transcobalamin II deficiency
Homocysteinuria
The clinical features of folate and cobalamin are alike in 2 presentations and differ in one.
Briefly discuss
•Folate deficiency:
✅Anemia
✅Atrophic glossitis
🚫neurologic changes
•Cobalamin deficiency:
✅Anemia
✅Atrophic glossitis
✅neurologic changes*
*cobalamin helps in myelination of nerves in the CNS, hence ⬇️cobalamin presents with neurologic changes
Do you know any other organs/tissues affected by megaloblastic anemia❓
Skin GI Genital system mucosal epithelium Congenital abnormalities (Neural tube defects) Neurologic changes Hyperhomocysteinemia
What are the clinical findings in B12 deficiency❓
Neurologic changes: Paresthesias Loss of position sense Ataxia ⬇️tendon reflexes Muscles weakness Loss of vibration sense (dorsal c) Spasticity Babinsky sign (lateral c) Romberg sign (dorsal c) Memory loss, dementia, confusion
Vitiligo Hyperpigmentation Greying of hair Weight loss Fever Diarrhea Constipation Splenomegaly
Giving folate to a B12 deficient pt may correct/prevent anemia but make neurologic deficits worse
True or false
True
To conclude a case of megaloblastic anemia, RBC indices should show❓
⬆️MCV
⬆️MCH
⬆️RDW
A peripheral smear of megaloblastic RBC would show❓
Macroovalocytosis
Anisocytosis, poikilocytosis
Bazophilic stippling
Howell-Jolly bodies, Cabot ring
Nucleated red cells
Neutrophil hypersegmentation
