Megalocyte Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Megalocyte and links to relevant pages within the course.
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| Pseudomacrocytes Another type of macrocyte can be seen in this image. Notice it appears larger than the lymphocyte but in contrast to the macrocytes (megalocytes) seen in megaloblastic anemias (vitamin B12 or folic acid deficiency), these macrocytes have an area of central pallor. These macrocytes are sometimes referred to as "pseudomacrocytes," since their size is the result of exaggerated flattening and thus the presence of central pallor. When this type of macrocyte is present on a blood slide, the MCV will most likely be within normal range. Pseudomacrocytes can be seen in peripheral blood smears from patients with cirrhosis of the liver, obstructive jaundice, post splenectomy and conditions that affect the red cell membrane. | View Page |
| Pseudomacrocytes Pseudo macrocytes, as well as some microcytes, can be seen in this slide. Notice that pseudomacrocytes do not have the oval appearance seen in some megalocytes. | View Page |
| The round and oval red cells with diameters of greater than 9 microns and decreased central pallor seen in this slide are example of: | View Page |
| The cell in the center of this slide would be a: | View Page |
| Summary of Macrocytes To summarize, two types of macrocytes can be seen, true macrocytes (megalocytes) and pseudomacrocytes. The MCV and MCH values will be increased when megalocytes are present, while all the indice values will be normal when pseudomacrocytes are found. | View Page |
| Megalocytes (macrocytes) are characterized by: (Choose ALL of the correct answers) | View Page |
| Macrocytes Macrocytes have a diameter of 9-14 microns (1.5 to 2 times larger than normal red cells) and the MCV is 100 fL or more. Several macrocytes are indicated by the arrows in this image. By comparison, macrocytes are larger than the nucleus of a normal lymphocyte. Macrocytes are frequently oval; two examples are indicated by the red arrows.Macrocytes are usually present in vitamin B12 and/or folic acid deficiencies. Decreased DNA synthesis causes the nucleus in the developing red cells to mature at a slower than normal rate. Since hemoglobin production is not affected, the mature red cell that is larger than normal is filled with hemoglobin, resulting in cells with little central pallor. Macrocytes are sometimes referred to as megalocytes. | View Page |
| The MCHC value is 39 gm/dl of RBC. Which of the following is the most likely explanation? | View Page |
| Hypochromia and Hyperchromia defined A decreased amount of hemoglobin is referred to as hypochromasia or hypochromia. MCHC values of 30% or less reflect this condition. Hyperchromasia and hyperchromia, refer to a hypothetical situation rather than an actual occurrence. The word, hyperchromia/sia, means increase in color; however the MCHC value cannot be higher than 36, since it is impossible for a cell to contain "too much" hemoglobin.Cells located in the "too thin" portion of the smear often appear to be "hyperchromic". Megalocytes (macrocytes), which appear to have increased amounts of hemoglobin, have an MCHC value within normal limits, indicating that the cells, although larger than normal, are normochromic. | View Page |