Hemoglobin (Hb or Hgb) is the protein in your red blood cells that carries oxygen. A low hemoglobin count is a below-average concentration of the oxygen-carrying hemoglobin proteins in your blood.
A low hemoglobin count is generally defined as less than 13.5 grams of hemoglobin per deciliter (135 grams per liter) of blood for men and less than 12 grams per deciliter (120 grams per liter) for women. In children, the definition varies with age and sex. The threshold differs slightly between medical practices.
A low hemoglobin count is a commonly seen blood test result. In many cases, a low hemoglobin count is only slightly lower than normal, isn't considered significant and causes no symptoms. A low hemoglobin count can also be caused by an abnormality or disease. In these situations, a low hemoglobin count is referred to as anemia.
The myeloproliferative neoplasms (MPNs), previously termed the myeloproliferative disorders, are characterized by the clonal proliferation of one or more hematopoietic cell lineages, predominantly in the bone marrow, but sometimes in the liver and spleen.
In contrast to myelodysplastic syndromes (MDS), MPNs demonstrate terminal myeloid cell expansion into the peripheral blood.
In the 2008 revision of the World Health Organization (WHO) classification of myeloid neoplasms, MPNs include: chronic myelogenous leukemia (CML), chronic neutrophilic leukemia, polycythemia vera (PV), primary myelofibrosis (PMF), essential thrombocythemia (ET), chronic eosinophilic leukemia, mastocytosis, and unclassifiable MPNs.
Overlap disorders (MDS/ MPN) are those chronic myeloid disorders unable to be classified as "classic" MPN or MDS. These include: chronic myelomonocytic leukemia (CMML), atypical CML, juvenile myelomonocytic leukemia, and unclassifiable MDS/MPN.