A Review of Hereditary Anemias for the Physician Assistant Exam
The Physician Assistant Exam (PANCE) may ask you about two basic hereditary causes of anemias: glucose-6-phosphate dehydrogenase (G6PD) deficiency and sickle cell anemia. Familiarize yourself with the basics of these.
G6PD deficiency is a hereditary condition in which the body is unable to produce enough glucose-6-phosphate dehydrogenase. It affects millions of people throughout the world, especially African-American males and people of Mediterranean descent.
Most kids with G6PD deficiency have no symptoms until their bodies are exposed to certain triggers or oxidative stresses. For the PANCE, be aware of the triggers: sulfa antibiotics, bacterial and viral illnesses, and medications used in the treatment of malaria, including primaquine phosphate (Primaquine) and dapsone.
Here’s how to recognize G6PD deficiency:
The diagnosis is based on a high clinical suspicion; tests can evaluate the degree of enzymatic activity, but they can also yield false-negative results.
You can see Heinz bodies on a peripheral smear.
Treatment consists of removing the offending trigger and transfusing as needed.
Sickle cell disease
Sickle cell disease causes the body to make blood cells that are sickle shaped in times of physical stress. Examples can include low-oxygen states, such as hypoxemia and pneumonia, as well as infection and dehydration. Sickle cell disease primarily affects people of African descent but can also affect people of Indian and Mediterranean heritage.
If you have sickle cell trait, you’re a carrier — you’ve inherited one gene for sickle hemoglobin and one normal gene, so you won’t develop any of the symptoms of sickle cell disease. People who have the sickle cell trait need to undergo genetic counseling to be aware of their risk of passing the sickle gene on to their children.
Here are some aspects of sickle cell disease to be aware of:
Sickle cell anemia is characterized by painful sickle cell crises, persistent anemia, and damage to organs of the body, including the heart, lungs, kidneys, and bones. Bone infarctions and avascular necrosis are long-term bone sequelae of sickle cell disease.
Sickle cell crisis can include vaso-occlusive crisis, aplastic crisis, sequestration crisis, and hemolytic crisis. An episode can last 5 to 7 days.
Sickle cell crisis is a life-threatening medical condition. Common precipitants include infection, any pulmonary process that causes hypoxemia, and volume-depleted states such as diarrhea. It can affect the lungs (acute chest syndrome), kidneys (kidney infarction), and bones (bone infarction). The treatment consists of oxygen, aggressive hydration, pain management, and folic acid supplementation. Exchange transfusions may also be needed.
Sickle cell disease comes in different types, including hemoglobin sickle cell disease. Hemoglobin electrophoresis can confirm the type of sickle cell.
People with sickle cell disease need chronic folic acid supplementation.
People who have sickle cell disease are at risk for recurrent infections, especially from encapsulated organisms, because of problems with opsonization. Therefore, people who have sickle cell disease need to keep up-to-date with immunizations, specifically the pneumococcal vaccine. Because of recurrent bone infarctions, these patients are also at risk for osteomyelitis.
In a patient with sickle cell disease, which of the following bacterial agents is a common cause of osteomyelitis?
(C) E. coli
The answer is Choice (D). People with sickle cell disease and Salmonella are very susceptible to bone infections. Of the other choices, Staph and Strep are also Gram-positive organisms that can cause osteomyelitis.