Hereditary Hemorrhagic Telangiectasia

Differential Diagnosis

HHT can be diagnosed either using clinical diagnostic criteria or by genetic testing for pathogenic mutations in ENG, ACVRL1 or SMAD4. Clinical diagnosis of HHT is made using the Curacao diagnostic criteria. These include: (1) recurrent, spontaneous epistaxis; (2) mucocutaneous telangiectasias; (3) visceral organ AVM; and (4) history of HHT in a first-degree relative. Patients who meet 3 or 4 criteria are said to have definite HHT, those with 2 criteria are classified as possible HHT, and those with 0 or 1 criteria are classified as unlikely HHT.27 The Curacao criteria have been validated in the adult population and have a sensitivity of 90% for the diagnosis of HHT.28 The Curacao criteria are of limited utility in the pediatric population given the age-dependent presentation of some of the criteria.29 We recommend genetic testing to identify the familial HHT mutation even if a patient meets clinical diagnostic criteria unless a familial mutation is already established. This is to facilitate diagnosis in at-risk family members, who may not manifest epistaxis or telangiectasias as yet (typically children and young adults) but may still have visceral AVMs and be at-risk for complications. Genetic testing will identify a mutation in ENG, ACVRL1, or SMAD4 in over 85% of patients with a clinical diagnosis of HHT.30