From the Guidelines
Microcytic erythrocytosis is a complex condition that requires a comprehensive diagnostic approach to identify the underlying cause, which may include hemoglobinopathies, iron deficiency, or myeloproliferative disorders, and management should focus on treating the underlying cause while monitoring for potential complications such as thrombosis. The diagnosis of microcytic erythrocytosis involves a combination of morphologic and kinetic approaches, including complete blood counts, reticulocyte count, and iron studies, as outlined in the guidelines for evaluating anemia 1. Key considerations in the diagnosis and management of microcytic erythrocytosis include:
- Identifying the underlying cause, which may involve genetic testing, hemoglobin electrophoresis, and bone marrow examination
- Monitoring for potential complications, such as thrombosis, and taking steps to prevent them, such as phlebotomy
- Managing iron deficiency cautiously in patients with myeloproliferative disorders to avoid exacerbating erythrocytosis
- Providing genetic counseling and supportive care for patients with hemoglobinopathies The most recent and highest quality study on this topic, published in 2014 in the journal Blood, provides practice guidelines for the diagnosis and management of microcytic anemias due to genetic disorders of iron metabolism or heme synthesis 1. These guidelines emphasize the importance of integrating clinical and molecular insights into daily practice to avoid unnecessary delay in diagnosis, invasive or costly diagnostic tests, and harmful treatments. In particular, the guidelines highlight the need for accurate and timely diagnosis of genetic anemias, such as sideroblastic anemias, in which iron overload can lead to severe morbidity and mortality. Overall, the management of microcytic erythrocytosis requires a careful and individualized approach, taking into account the underlying cause and potential complications, and should be guided by the most recent and highest quality evidence available.
From the Research
Definition and Causes of Microcytic Erythrocytosis
- Microcytic erythrocytosis refers to a condition where there is an increase in the number of red blood cells (erythrocytosis) with a mean corpuscular volume (MCV) of less than 80 µm3 (80 fL) in adults 2.
- The most common causes of microcytosis are iron deficiency anemia and thalassemia trait, with other diagnoses including anemia of chronic disease, lead toxicity, and sideroblastic anemia 2.
- Microcytic polycythemia can also occur in patients with chronic hypoxia, where supplemental iron is often required to maintain the increased red blood cell mass, but iron deficiency with microcytic polycythemia can develop if iron is withheld or if blood withdrawal worsens the iron deficiency 3.
Evaluation and Diagnosis
- Serum ferritin measurement is the first laboratory test recommended in the evaluation of microcytosis, with low ferritin levels suggesting iron deficiency 2.
- Further evaluation may include total iron-binding capacity, transferrin saturation level, serum iron level, and possibly hemoglobin electrophoresis to differentiate between iron deficiency anemia and thalassemia trait 2.
- In cases of erythrocytosis, measurement of the erythropoietin level is a first step, with a low erythropoietin level indicating a primary cause and a normal or elevated level indicating a secondary etiology 4.
Management and Treatment
- The combination of frequent phlebotomy with oral iron therapy may improve iron stores while safely maintaining a stable hematocrit level in patients with microcytic polycythemia, with beneficial effects on tissue oxygen delivery and utilization 3.
- In cases of iron deficiency anemia, treatment with iron supplementation is necessary, but the underlying source of the deficiency should be determined, with the possibility of gastrointestinal malignancy considered 2.
- For patients with thalassemia trait, no specific treatment is usually required, but genetic counseling may be necessary 2.
Related Conditions
- Macrocytosis, or an increased MCV, can also occur in patients with chronic obstructive pulmonary disease (COPD), with the cause of the elevation in MCV remaining elusive 5.
- Erythrocytosis can be classified as primary or secondary, congenital or acquired, with polycythemia vera being the most common primary acquired disorder 4.