This can result in serious damage to such organs as the lung, heart, kidneys, and brain. Classification
Based on their causes, hypereosinophilias can be sorted into subtypes. However, cases of eosinophilia, which exhibit eosinophil counts between 500 and 1,500/μL, may fit the clinical criteria for, and thus be regarded as falling into, one of these hypereosinophilia categories: the cutoff of 1,500/μL between hypereosinophilia and eosinophilia is somewhat arbitrary. There are at least two different guidelines for classifying hypereosinophilia/eosinophilia into subtypes. The General Haematoloy and Haemato-oncology Task Forces for the British Committee for Standards in Haematology classifies these disorders into a) Primary, i.e. caused by abnormalities in the eosinophil cell line; b) Secondary, i.e. caused by non-eosinophil disorders; and c) Idiopathic, cause unknown. The World Health Organization classifies these disorders into a)  Myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1 (i.e. high eosinophil blood counts caused by mutations in the eosinophil cell line of one of these three genes), b) Chronic eosinophilic leukemia, and c) the Idiopathic hypereosinophiic syndrome. In the latter classification, secondary hypereosinophilia/eosinophilia is not viewed as a true disorder of eosinophils. Here these two classifications are merged and expanded to include the many forms of secondary, i.e. reactive hypereosinophilia/eosinophilia, disorders and also includes another subtype, organ-restricted hypereosinophilias, a disorder in which eosinophil-mediated tissue damage is restricted to one organ and is often but not always associated with increased blood eosinophil counts. Primary hypereosinophilia
Primary hypereosinophilia is due to the development of a clone of eosinophils, i.e.
A translocation between chromosomes 5 and 14 in patients with acute B lymphocytic leukemia resulted in the juxtaposition of the IL-3 gene and the immunoglobulin heavy-chain gene, causing overproduction production of IL-3, leading to blood and tissue eosinophilia. Primary immunodeficiency diseases
Primary immunodeficiency diseases are inborn errors in the immune system due to defective genes. Certain of these disorders are sometimes or often associated with hypereosinophilia. The list of such disorders includes ZAP70 deficiency (defective  ZAP70 gene), CD3gamma chain deficiency (defective CD3G gene), MCHII deficiency (defective RFXANK gene), Wiskott–Aldrich syndrome (defective WAS gene), IPEX syndrome (defective IPEX gene), CD40 gene defect, and autoimmune lymphoproliferative syndrome (defective Fas receptor gene). More than 30 other primary immunodeficiency diseases are sometimes associated with modest increases in eosinophil counts, i.e. eosinophilia. The hyperimmunoglobulin E syndrome is associated with hypereosinophilia or eosinophilia due to mutations in any one of the following genes: STAT3, DOCK8, PGM3, SPINK5, and TYK2 (see mutations in the hymperimmoglobulin E syndrome). Omenn syndrome is a severe combined immunodeficiency disease characterized by skin rash, slenomegaly, and lymphadenopathy due to a causative mutation in RAG1, RAG2, or, more rarely, one of several other genes. Lymphocyte-variant hypereosinophilia
Lymphocyte-variant hypereosinophilia is a disorder attributed to the expansion of a cytokine-producing, aberrant population of a particular T-cell phenotype. The disorder is clonal with regard to the
production of abnormal T-cell lymphocytes not eosinophils which appear phenotypically normal.