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USMLE Step2 Secrets Hematology General


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Medications that cause anemia

What can cause RBC antibodies with subsequent hemolysis?
methyldopa, penicillins, sulfa drugs
Medications that cause anemia

What can cause hemolysis in patients with glucose-6-phosphatase deficiency?
chloroquine and sulfa drugs
Medications that cause anemia

What can cause megaloblastic anemia through interference with folate metabolism?
Medications that cause anemia

What can cause aplastic anemia and bone marrow suppression?
Chloramphenicol, cancer drugs and zidovudine.
What are the causes of microcytic anemia with normal or elevated retic count?
thalassemia/hemoglobinopathy (e.g., sickle cell disease)
What are the causes of microcytic anemia with low retic count?
iron deficiency
anemia of chronic diesease (some cases)
sideroblastic anemia
lead poisoning
What are the causes of macrocytic anemia?

Note: all types of macrocytic anemia have low retic count
folate deficiency
vit B12 deficiency
medications (methotrexate, phenytoin)
cirrhosis, liver disease
alcohol abuse (interferes with folate use)
What are the causes of normocytic anemia with normal or elevated retic count?
acute blood loss
hemolytic (multiple causes)
medications (antibody-causing)
What are the causes of normocytic anemia with low retic count?
cancer/dysplasia (e.g. myelophthisic, acute luekemia
anemia of chronic disease (some cases)
aplastic anemia/meciations causing bone marrow suppresions
endocrine failure (thyroid, pituiatry)
renal failure
What are the classic lab abnormalities in iron deficiency anemia?
low iron
low ferritin
elevated TIBC (aka transferrin)
low TIBC saturation
How is thalassemia differentiated from iron deficiency?
both cause microcytic hypochromic anemai, but thalassemai must be differentiated from iron deficiency because iron levels are normal in thalassemia.

Iron supplementation is contraindicated in patients with thalassema because it may cause iron overload.

Look of elevations in hemoglobin A2 and hemoglobin F (beta thalassemia only)

Look for target cells, nuclated RBCs, diffuse basophilia on peripheral smears.

Skull radiograph with "crew-cut" appearnce; extramedullary hematopoiesis

Also look for splenomegaly and positive family history (thalssemia is more common in blacks, Mediterraneans, and Asians)
How can sideroblastic anemia be recognized on the Step 2 exam?
The typical description is a microcytic, hypochromic anemia with the following labs:

increased or normal iron
increased or normal ferritin
increased or normal TIBC (transferrin)

This description should immediately steer you away from iron deficiency.

Look for polychromatophilic stippling and the classic "ringed sideroblast" in the bone marrow.
Should the presnse of sideroblastic anemia raise concern about other conditions?
Sideroblastic anemia may be related to myelodysplasia or future blood dyscrasia. Although probably you will not be asked about management, treatment is supportive. In rare cases, the anemai responds to pyridoxine. Do not give iron.
How you recognize anemia of chronic disease?
First look for the presence of a disease that causes chronic inflammation (e.g. rheumatoid arthritis, lupus erythematosus, cancer, tuberculosis).

In terms of labs, the anemia is either microcytic or normocytic.

Serum iron is low, but so is TIBC (transferrin). Thus, the percent saturation may be near normal. Serum ferritin is elevated (because ferritin is an acute-phase reactant, the level should be increased).

Treat the underlying disorder to correct the anemia. Do not give iron.
What is Plummer-Vinson syndrome?
A triad of unknown etiology:
esophageal web resulting in dysphagia
iron deficiency anemia
What are causes of folate deficiency?
Folate deficiency is commonly seen in alcoholics (poor intake) and pregnant women (increased need).

Rare causes of folate deficiency include:
poor diet (tea and toast)
drugs (methotrexate, phenytoin)
Both folate and vitamin B12 deficiency cause macrocytic anemia, but what differentiaties them clinically?
In vit B12 deficiency, patients have neurologic symptoms.

The neurologic symptoms consist of loss of sensation and position sense, paresthesias, ataxia, spasticity, hyperreflexia, positive Babinski sign, dementia.

In folate deficiency, patients do not have neurologic symptoms.
In a smear, what should you seen in folate deficiency?
macrocytes and hypersegmented neutrophils with NO neurologic symptoms or signs and low folate leves in serum or RBCs.

Treat with oral folate.
What is the most common cause of vit B12 deficiency?
Pernicious anemia, caused by antiparietal cell antibodies. Achlorhydria (no stomach acid secretion and elevated stomach pH) and antibodies to parietal cells are generally present in pernicious anemia.
What else may cause vit B12 deficiency besides pernicious anemia?
gastretomy, terminal ileum resection or disease (Crohn's disease), strict vegan diet, chronic pancreatitis, and the infamous fish tapeworm Diphyllobothrium latum.
What test can you use to identify the etiology of vit B12 deficiency?
a Schilling test
How is vit B12 deficiency treated?
supplementation via parenteral (intramuscular injection) because most patients cannot absorb the vitamin through the gut.

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