Granulocytosis

Granulocytes are white blood cells which contain granules. Granulocytosis could be due to an increase in neutrophil count (neutrophilia), an increase in eosinophil count (eosinophilia), or an increase in basophil count (basophilia). The neutrophil count increases by a number of mechanisms including increased production in the bone marrow, increased release from bone marrow storage sites, increase in demargination into circulation, decrease in egress from circulation, and decrease in margination. Each of these mechanisms of neutrophilia has many causes, and often a single etiology may result in neutrophilia through multiple mechanisms. The most common type of neutrophilia is reactive neutrophilia and can be acute or chronic. Primary neutrophilia is uncommon and results from abnormal regulation of neutrophil production in the bone marrow. Eosinophilia is not as common as neutrophilia. The most common cause of eosinophilia in the USA is allergic disorders, while in developing countries, it is the parasitic infestations. In familial eosinophilia syndrome, eosinophilia occurs in otherwise healthy patients due to an imbalance in eosinophil production. Isolated basophilia is rare but is seen in patients with iron deficiency anemia, chronic inflammatory conditions, and some infections. Identifying and treating the underlying cause appropriately resolves granulocytosis in most instances.