The Curaçao criteria were developed in 1999 for the diagnosis of HHT. Global consensus guidelines for screening have been developed by HHT experts and follow evidence-based data when available. Genetic testing can be performed, but not every genetic mutation for HHT has been identified; therefore, some cases of HHT cannot be detected with current laboratory testing. If a mutation is found in one affected person, then other family members can be tested to determine if they carry the same mutation. The absence of the known mutation eliminates the need to screen for other manifestations of the disease. This can be especially helpful for children of affected parents because performing some of these tests may be more difficult and may require sedation or general anesthesia. Children of a parent with HHT who do not meet the criteria for a diagnosis of HHT should be considered to have the disease, unless excluded by genetic testing, for purposes of screening.
The established clinical diagnostic criteria for HHT are:
- Nosebleeds (epistaxis), which are spontaneous and recurrent (may be mild or severe).
- Telangiectases on the skin or mucous membranes (mucocutaneous). Characteristic sites include the lips, oral cavity, fingers, and nose.
- Visceral arteriovenous malformations (AVMs), which may be located in the lungs, brain, liver, spinal cord, and GI tract.
- A first-degree relative with HHT, based on these diagnostic criteria.
A diagnosis of HHT is considered definite when three or more of these features are present, possible or suspected when two findings are present, and unlikely with fewer than two findings.
Clinical genetic testing for HHT is available through four labs in North America: University of Pennsylvania, ARUP University of Utah, HHT Solutions Toronto Canada, and Hospital for Sick Children.