Can ENG Mutations Be Acquired?
No, ENG (endoglin) mutations causing hereditary hemorrhagic telangiectasia (HHT) are inherited, not acquired—HHT is an autosomal dominant genetic disease where mutations are passed from parent to child or arise as de novo germline mutations, not acquired during a person's lifetime.
Inheritance Pattern and Mutation Origin
HHT is definitively characterized as an autosomal dominant disease where ENG mutations are germline (present from conception), not somatic (acquired after birth) 1. The evidence demonstrates:
- In 97% of patients with definite clinical HHT diagnosis, a causative mutation is identified in ENG, ACVRL1, or SMAD4 genes 1
- These mutations are inherited in an autosomal dominant pattern, meaning only one mutated copy from either parent causes disease
- The genetic basis is established at conception, not acquired through environmental exposures or aging
De Novo Mutations: The Exception That Proves the Rule
While ENG mutations are not "acquired" in the traditional sense, de novo mutations can occur—but these still arise in the parental germline (sperm or egg cells), not in the affected individual's somatic cells 2:
- One documented case identified a de novo deletion in exon 7 of ENG that occurred in the paternal germline 2
- The patient inherited this new mutation from their father's gamete, but the father himself was unaffected
- This represents a germline mutation event, not an acquired somatic mutation
Clinical Implications
For Diagnosis:
- Genetic testing identifies ENG mutations in affected individuals and at-risk family members 1
- The Curaçao clinical criteria remain the diagnostic standard, with genetic testing primarily for asymptomatic persons from families with known HHT 1
- Multiple novel ENG mutations continue to be identified in families worldwide 3, 4, 5
Common Pitfalls to Avoid:
- Do not confuse germline mutations with acquired/somatic mutations—HHT is not caused by environmental exposures or lifestyle factors
- Do not overlook family history—even in apparent "sporadic" cases, de novo germline mutations may be present 2
- Do not assume negative family history excludes HHT—approximately 20% of cases result from de novo mutations
Mutation Mechanisms:
The functional analysis reveals ENG mutations cause disease through different mechanisms 6:
- Loss of BMP9 binding capacity
- Defective protein trafficking to cell surface
- Retention in endoplasmic reticulum
- Dominant-negative effects where mutant protein impairs wild-type endoglin function
The key distinction: ENG mutations are constitutional (present in all cells from conception), not acquired during life, making HHT a hereditary rather than acquired vascular disorder.