USMLE® Step 1 style questions USMLE
A 65-year-old woman comes to the clinic because of shortness of breath and fatigue for the past 2 months. The patient states that she feels tired all day and has little energy to get out of bed. She also reports frequently stopping to catch her breath after climbing a flight of stairs. Past medical history is significant for breast cancer treated with chemoradiotherapy 10 years ago. Family history is noncontributory. Temperature is 37.0°C (98.6°F), pulse is 101/min, respirations are 20/min, and blood pressure is 135/85 mmHg. Physical examination shows mucosal pallor but no lymphadenopathy. Laboratory evaluation reveals:
|Complete blood count|
Peripheral blood smear is shown below:
Reproduced from: Wikimedia Commons
Which of the following is the most likely diagnosis in this patient?
Myelodysplastic syndromes exam links
Content Reviewers:Yifan Xiao, MD
Myelodysplastic syndromes, or MDS, are a group of rare blood disorders associated with faulty development of blood cells in the bone marrow.
MDS can affect individuals of all ages, but it’s more common after the age of 60.
Blood cells develop from hematopoietic stem cells, through a process called hematopoiesis.
This involves a number of divisions, and eventually, results in three types of blood cells: red blood cells, which carry oxygen around our bodies, white blood cells to help fight disease causing pathogens, and platelets that help form clots to stop bleeding.
Once these cells are fully mature, they leave the bone marrow and enter the bloodstream.
In MDS, hematopoietic stem cells are damaged, so they give rise to faulty blood cells, which don’t mature, but instead persist as immature cells, called blasts.
These immature blood cells usually die in the bone marrow or soon after they go into the blood, so you can’t really count on them to do the job of mature blood cells.
As the condition progresses, immature blood cells gradually take over the bone marrow, which displaces and reduces the normal ones.
In most cases, the cause of MDS is not known.
When this happens, it's classified as primary MDS.
In rare cases, they can be caused by chemo or radiation therapy, and this is called secondary MDS.
MDS comprises a spectrum of diseases with differing potential for remaining stable or progressing to acute myeloid leukemia, or AML.
The most common feature of MDS is anemia, caused by low red blood cell levels.
Symptoms of anemia include dizziness, irritability, headaches, and pale skin.
Low white blood cell levels increase the risk of bacterial and fungal infections.
Finally, low levels of platelets cause excessive bruising following minimal injury and easy bleeding.
Now, MDS usually worsens with time, as normal bone marrow function diminishes.
40-50 percent of the time, MDS deteriorates into a form of cancer known as acute myeloid leukemia, or AML.
This happens when there are more than 20% blasts in the bone marrow.
Diagnosis requires a variety of specialized tests including complete blood counts, a peripheral blood smear, as well as bone marrow aspiration and biopsy.
On a complete blood count, there may be low levels of one, two or all of the three blood cell types.
On a peripheral blood smear, there may be big and oval-shaped red blood cells and abnormal white blood cells and platelets.
The bone marrow sample may show an increase in cell count with dysplastic changes in the three blood cell types.
Myelodysplastic syndromes or just MDS, refer to a group of disorders in which the bone marrow does not produce enough healthy blood cells, usually for unknown causes. Symptoms can include fatigue, shortness of breath, and an increased risk of infection and bleeding. Treatment options for MDS include medications, transfusions, and bone marrow transplantation, depending on the severity of the condition.
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