Lecture 3: Macrocytic Anemias Flashcards
What is Macrocytic anemia?
larger than normal erythrocytes with insufficient amount of Hgb
What is Megaloblastic anemia? What are the values?
- Decreased folate or vitamin B12
~ ineffective RBC production (WBC and PLT too)
~ vitamin B12 only –> defect in myelin formation
–> neurological - Slows DNA production (interferes with cell growth and nuclear malformation)
- MCV >100
- Macroovalocytes
- Hypersegmented neutrophils
How do people with Megoblastic anemia present?
Many patients are asymptomatic
- non-specific signs of anemia
- Glossitis
- Angular cheliosis
- Dyspepsia (B12)
- Neurologic problems (B12)
- Muscle weakness
- Ataxia
- Incontinence
- Dementia-like symptoms
Classic presentation of B12 deficiency
(1) Severe anemia- Hgb 100
(3) (+/-) neurologic signs and symptoms
Why would you test B12 as part of the workup for neuropathy or dementia?
Because neuro symptoms can occur before anemia develops
Vitamin B12
- Comes from animal products
- Stored in the liver
~ 2-5 mg stored
~ 6-9 mcg minimum daily requirement
How long does it take to develop a deficiency after absorption of B12 ceases?
Months to years
Most vitamin B12 deficiencies are due to what?
Malabsorption
VItamin B12 deficiency: DDx (4)
(1) Intestinal malabsorption (#1 cause)
- Crohn’s disease, pancreatic insufficiency,
sprue, alcohol, antacids
(2) Surgery or radiation to stomach or ileum
(3) Dietary deficiency (rare in US- strict vegetarians)
(4) Pernicious anemia (mostly older adults)
Pernicious anemia
- Average age 60
- 1/7500 develop per year
- Gastric atrophy
- Anti-parietal cells Ab
- Anti- IF Ab
- Lack of intrinsic factor
Folate
- comes from animal products and green leafy vegetables, fruits, nuts, meats, grains
- daily requirement 200-400 mcg
- many grain products are fortified
Folate deficiency: DDx
- Dietary lack (green leafy vegetables)
~ Alcoholism
~ Chronic debilitating illness (elderly) - Demand > Availability
~ pregnancy, hemolysis, sickle cell disease - Intestinal malabsorption
~ jejunum - Drugs (sulfa, trimethoprim, phenytoin, phenobarbital, methotrexate, HIV drugs)
How do you diagnose a megaloblastic anemia?
- Smear
~ macro-ovalcytes
~ hypersegmentation
- Vitamin B12 level
- Folate level
- LDH (may be high due to cell turnover)
- Reticulocyte count (low to normal)What will the MMA and HC labs be with B12 deficiency?
BOTH increased
What will the MMA and HC labs be with Folate deficiency?
MMA (Methylmalonic acid)- Normal
HC (Homocysteine)- Increased
