 Genetic tests are available for the ENG , ACVRL1 and MADH4 mutations . Testing is not always needed for diagnosis , because the symptoms are sufficient to distinguish the disease from other diagnoses . There are situations in which testing can be particularly useful . Firstly , children and young adults with a parent with definite HHT may have limited symptoms , yet be at risk from some of the complications mentioned above ; if the mutation is known in the affected parent , absence of this mutation in the child would prevent the need for screening tests . Furthermore , genetic testing may confirm the diagnosis in those with limited symptoms who otherwise would have been labeled " possible HHT " ( see below ) . 
