Eosinophil peroxidase deficiency is a condition that affects certain white blood cells called eosinophils but causes no health problems in affected individuals. Eosinophils aid in the body's immune response. During a normal immune response, these cells are turned on (activated), and they travel to the area of injury or inflammation. The cells then release proteins and other compounds that have a toxic effect on severely damaged cells or invading organisms. One of these proteins is called eosinophil peroxidase. In eosinophil peroxidase deficiency, eosinophils have little or no eosinophil peroxidase. A lack of this protein does not seem to affect the eosinophils' ability to carry out an immune response.

Because eosinophil peroxidase deficiency does not cause any health problems, this condition is often diagnosed when blood tests are done for other reasons or when a family member has been diagnosed with the condition.

Approximately 100 individuals with eosinophil peroxidase deficiency have been described in the scientific literature. Based on blood test data, varying estimates of the prevalence of the condition have been reported in specific populations. Eosinophil peroxidase deficiency is estimated to occur in 8.6 in 1,000 Yemenite Jews, in 3 in 1,000 North-African Jews, and in 1 in 1,000 Iraqi Jews. In northeastern Italy, the condition occurs in approximately 1 in 14,000 individuals; in Japan it occurs in 1 in 36,000 people; and in Luxembourg, eosinophil peroxidase deficiency is thought to occur in 1 in 100,000 people.

Mutations in the EPX gene cause eosinophil peroxidase deficiency. The EPX gene provides instructions for making the eosinophil peroxidase protein. During an immune response, activated eosinophils release eosinophil peroxidase at the site of injury. This protein helps form molecules that are highly toxic to bacteria and parasites. These toxic molecules also play a role in regulating inflammation by fighting microbial invaders.

EPX gene mutations reduce or prevent eosinophil peroxidase production or result in a protein that is unstable and nonfunctional. As a result, eosinophils have severely reduced amounts of eosinophil peroxidase or none at all. Other proteins within affected eosinophils are normal, and while the cells lacking eosinophil peroxidase are smaller and may have structural changes, the loss of eosinophil peroxidase does not appear to impair the function of eosinophils.

Genetic Testing Information

• Genetic Testing Registry: Eosinophil peroxidase deficiency

Genetic and Rare Diseases Information Center

• Eosinophil peroxidase deficiency

Patient Support and Advocacy Resources

• National Organization for Rare Disorders (NORD)

Catalog of Genes and Diseases from OMIM

• EOSINOPHIL PEROXIDASE DEFICIENCY; EPXD

Scientific Articles on PubMed

• PubMed

• Kutter D, Mueller-Hagedorn S, Forges T, Glaesener R. A case of eosinophil peroxidase deficiency. Ann Hematol. 1995 Dec;71(6):315-7. doi: 10.1007/BF01697987. Citation on PubMed
• Nakagawa T, Ikemoto T, Takeuchi T, Tanaka K, Tanigawa N, Yamamoto D, Shimizu A. Eosinophilic peroxidase deficiency: Identification of a point mutation (D648N) and prediction of structural changes. Hum Mutat. 2001 Mar;17(3):235-6. doi: 10.1002/humu.10. Citation on PubMed
• Romano M, Patriarca P, Melo C, Baralle FE, Dri P. Hereditary eosinophil peroxidase deficiency: immunochemical and spectroscopic studies and evidence for a compound heterozygosity of the defect. Proc Natl Acad Sci U S A. 1994 Dec 20;91(26):12496-500. doi: 10.1073/pnas.91.26.12496. Citation on PubMed or Free article on PubMed Central
• Zabucchi G, Soranzo MR, Menegazzi R, Vecchio M, Knowles A, Piccinini C, Spessotto P, Patriarca P. Eosinophil peroxidase deficiency: morphological and immunocytochemical studies of the eosinophil-specific granules. Blood. 1992 Dec 1;80(11):2903-10. Citation on PubMed