Anemia differentials Flashcards
Lab test result to look for when anemia is noted in a patient
- MCV < 80 fL (microcytic)
- MCV 80–100 fL (normocytic)
- MCV > 100 fL (macrocytic)
Causes of microcytic anemia
- Sideroblastic anemia
- ACD
- Lead poisoning
- Thalassemias
- IDA (late)
Causes of macrocytic anemia
- Megaloblastic
- Orotic aciduria
- B12 deficiency
- Folate deficiency
- Non-megaloblastic
- Liver disease
- Alcoholism
- Diamond-Blackfan anemia
- Memory aid:*
- OBF LADi eagles!
How to differentiate between normocytic anemia?
- Reticulocyte count
- Normal or decreased
- Non-hemolytic
- Increased
- Hemolytic
- Normal or decreased
Non-hemolytic causes of normocytic anemia
- ACD
- Chronic kidney disease
- Iron deficiency (early)
- Aplastic anemia
How to differentiate between hemolytic causes of anemia?
- Intrinsic
- RBC membrane defect: hereditary spherocytosis
- RBC enzyme deficiency: G6PD, pyruvate kinase
- HbC disease
- Paroxysmal nocturnal hemoglobinuria
- Sickle cell anemia
- Extrinsic
- Autoimmune
- Microangiopathic
- Macroangiopathic
- Infections
Memory aid:
-
In from SG to PH twice
- Sickle cell anemia
- G6PD
- Paroxysmal nocturnal hemoglobinuria
- Pyruvate kinase deficiency
- Hereditary spherocytosis
- HbC disease
Why is the mean corpuscular volume increased in megaloblastic macrocytic anemia?
There is a defect in DNA synthesis: the nucleus takes longer to mature than the cytosol and thus there is excess cytoplasm, creating a megaloblast; this is caused by B12 and folate deficiency
A patient has anemia with a mean corpuscular volume of 110 fL and glossitis and on the peripheral smear you note hypersegmented neutrophils; what are the two possible causes of this condition?
B12 or folate deficiency; both present with these features
What laboratory test (other than a vitamin level) will distinguish between B12 and folate deficiency as a cause of megaloblastic anemia?
- Methylmalonic acid is elevated in B12 deficiency but normal in folate deficiency
- Homocysteine is elevated in both deficiencies
What kind of anemia is associated with congenital deficiencies in purine or pyrimidine synthesis?
Macrocytic anemia (eg, orotic aciduria) because of the relative delay in nucleus maturation compared to cytoplasm
Name five medications that can cause macrocytic anemia
- Methotrexate
- Trimethoprim
- Fluorouracil
- Zidovudine
- Hydroxyurea
What change in mean corpuscular volume would you expect in an otherwise healthy patient who has had moderate to severe blood loss?
Increased mean corpuscular volume, because the patient will compensate with reticulocytosis, which have slightly higher mean corpuscular volumes than mature red blood cells
What kind of anemia is seen in a patient with poor dietary vitamin intake?
Macrocytic anemia, due to B12 or folate deficiency (remember that alcoholics are also often malnourished)
Anemia caused by veganism
Vitamin B12 deficiency anemia
How are normocytic, normochromic hemolytic anemias further classified?
First by cause: intrinsic vs extrinsic to the red blood cell; and then by location: intravascular vs extravascular
Name three causes of normocytic, normochromic anemia that are not due to hemolysis
- Anemia of chronic disease
- Renal disease (decreased erythropoietin)
- Aplastic anemia (bone marrow failure)
Memory aid:
-
Normal non-hemolytic
- ARA
Name six causes of normocytic, normochromic hemolytic anemia that are intrinsic to the red blood cell
- Hereditary spherocytosis
- G6PD
- Pyruvate kinase deficiency
- Sickle cell anemia
- Hemoglobin C defect
- Paroxysmal nocturnal hemoglobinuria
Name three causes of normocytic, normochromic hemolytic anemia that are extrinsic to the red blood cell
- Autoimmune hemolysis
- Microangiopathies like disseminated intravascular coagulation or thrombotic thrombocytopenic purpura–hemolytic uremic syndrome
- Infections
What is a cause of normocytic, normochromic hemolytic anemia that is intrinsic to the red blood cell and occurs in the intravascular space?
Paroxysmal nocturnal hemoglobinuria
Name two causes of normocytic, normochromic hemolytic anemia that are extrinsic to the red blood cell and occur in the extravascular space
Autoimmune hemolysis due to warm agglutinins (not cold) or microangiopathies like disseminated intravascular coagulation or thrombotic thrombocytopenic purpura–hemolytic uremic syndrome
Generally, hemolysis that is intrinsic to the red blood cell occurs in the _____ (intravascular/extravascular) space, whereas hemolysis extrinsic to the red blood cell occurs in the _____ (intravascular/extravascular) space with the exception of ____ which is intrinsic and intravascular and ____ which is intrinsice but exhibits both intra- and extravascular hemolysis
- Extravascular
- Intravascular
- Paroxysmal nocturnal hemoglobinuria
- G6PD
T/F. All extrinsic types of hemolytic anemia exhibit intravascular hemolysis
True
Hemolysis can lead to what lab findings?
Increases in LDH, reticulocytes, unconjugated bilirubin, urobilinogen in urine
Intravascular hemolysis
- Lab findings
- Associated disease
- Lab findings
- ↓ haptoglobin
- ↑ schistocytes on blood smear
- Characteristic hemoglobinuria, hemosiderinuria, and urobilinogen in urine
- ↑ unconjugated hemoglobin
- Associated disease
- Mechanical hemolysis (eg, prosthetic valve)
- Paroxysmal nocturnal hemoglobinuria
- Microangiopathic hemolytic anemias
Extravascular hemolysis
- Findings
- Associated pathology
- Findings
- Spherocytes in peripheral smear
- Associated pathology
- Hereditary spherocytosis
- Autoimmune hemolytic anemia
