*3.5. Anemia*

A history of anemia was reported in 28/205 (13.7%) patients. No genotype was significantly associated with current or historical anemia (*p* = 0.735). Notably, history of anemia was not significantly associated with epistaxis or GI bleeding.

#### *3.6. Organ Vascular Malformations*

Pulmonary AVMs were reported in 62/205 (30.2%) patients in our cohort. Brain VMs were reported in 70/205 (34.1%) patients. Pediatric patients with an *ENG* mutation were significantly more likely to have pulmonary AVMs (*p* < 0.001) and brain VMs (*p* < 0.001). Patients with an *ENG* mutation were also more likely to have any organ VM (pulmonary, brain, liver) compared to patients with *ACVRL1* or *SMAD4* mutations (*p* < 0.001). While a higher proportion of patients with an *ACVRL1* mutation had liver VMs compared to patients with an *ENG* gene mutation, this was not statistically significant (*p* = 0.093).

#### *3.7. Combined Phenotype*

Thirty-three (16.1%) of patients in our cohort had a combined phenotype, characterized by the presence of both pulmonary AVM(s) and brain VM(s). The majority (72.7%) of the patients with this combined phenotype had an *ENG* mutation and this association was found to be statistically significant (*p* < 0.001). Notably, sex was not a risk factor for the combined phenotype; 17/33 patients (51.5%) with a combined phenotype were male.
