How does eosinophil peroxidase deficiency affect blood test interpretation, especially eosinophil counts or related markers?

Standard complete blood counts will show normal eosinophil numbers. However, some specialized labs that measure eosinophil peroxidase activity may report low or absent activity. It is important for clinicians to note that low peroxidase activity in the context of normal eosinophil counts is a benign genetic variant and does not indicate eosinophil dysfunction.

If a family member has eosinophil peroxidase deficiency, should other relatives be tested, and what does the test involve?

Because the condition is inherited in an autosomal recessive pattern, siblings and parents of an affected individual are at risk of being carriers. Genetic counseling is recommended, followed by a blood test that measures eosinophil peroxidase activity and sequencing of the EPX gene to confirm the mutation. The test is a simple blood draw and does not require special preparation.

Does eosinophil peroxidase deficiency increase the risk of allergies, asthma, or other immune disorders?

Current evidence indicates that individuals with eosinophil peroxidase deficiency do not have an increased risk of allergic diseases or asthma. Their eosinophils can still perform normal immune functions, so the deficiency is considered clinically silent.

Can lifestyle or dietary changes help compensate for the lack of eosinophil peroxidase?

No specific lifestyle or dietary modifications are needed. Maintaining a balanced diet and a healthy lifestyle supports overall immune health, but there is no evidence that supplements or special diets can replace the missing enzyme.

Eosinophil peroxidase deficiency

A rare genetic disorder that reduces a key eosinophil protein but does not cause health problems, often discovered incidentally during routine blood tests.

Overview

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 . 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.

Frequency

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.

Causes

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.

Learn more about the gene associated with Eosinophil peroxidase deficiency

Inheritance

This condition is inherited in an , which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Other Names for This Condition

EPXD
Peroxidase and phospholipid deficiency in eosinophils
Presentey anomaly

Additional Information & Resources

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

References

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