Effects of Pazopanib on Hereditary Hemorrhagic Telangiectasia Related Epistaxis and Anemia (Paz)

During the Efficacy Study (Part B), the investigators will study whether Pazopanib, taken daily for 24 weeks, will reduce the severity of nose bleeds in patients with hereditary hemorrhagic telangiectasia (HHT). Patients will either be provided active drug or a placebo \[sugar - inactive pill\], and be tested for nose bleed severity throughout the trial, including particularly nose bleed duration. Investigators will also test for blood loss, as well as for safety. This study is funded by the US Department of Defense USAMRAA and FDA/OOPD.

Part B Inclusion Criteria (all of the following are necessary): * A definite or probable diagnosis of hereditary hemorrhagic telangiectasia (HHT): 1. Definite clinical HHT defined as having at least 3 of the following criteria: * Spontaneous and recurrent epistaxis. * Multiple telangiectasias at characteristic sites: lips, oral cavity, fingers, nose. * Visceral lesions: GI telangiectasia, pulmonary, hepatic, cerebral or spinal AVMs. * A first degree relative with HHT according to these criteria. 2. OR a definite diagnosis of HHT based on a pathogenic genetic mutation for HHT. 3. OR probable HHT based on having 2 of the above criteria with high clinical suspicion of HHT. * Stable IV iron use and/or blood transfusions stable for 12 weeks prior to test product initiation. * Must agree not to undergo cautery of nasal telangiectasias or to start new therapies for HHT while on study. * Women of childbearing potential must agree to abstinence or to use an acceptable double method contraception until 4 weeks after drug termination. Pregnancy testing will be done throughout the trial. * Men are mandated to use condoms. * Capable of giving signed informed consent. * Able and willing to return for outpatient visits at the protocol specified intervals. * Able and willing to complete blood pressure monitoring at home. * Able and willing to complete daily patient reported outcome measurements at home. * Must meet all of the inclusion criteria for either: Severe Anemia Cohort: i. Anemia mainly due to HHT (in the judgment of the PI) with average Hgb \460 msec for women, based on averaged QT corrected interval values of triplicate ECGs obtained over a brief recording period. * History of familial prolonged QT. * Any concomitant medication which is known to prolong QT. * Average baseline hemoglobin \ 1.5x ULN or activated partial thromboplastin time (aPTT) \> 1.5x ULN (unless due to known concurrent medications, e.g. warfarin). * Alanine Transaminase (ALT) \>2 x upper limit of normal. * Bilirubin \>1.5x upper limit of normal (isolated bilirubin \>1.5x upper limit of normal is acceptable if bilirubin is fractionated and direct bilirubin \< 35%). * Participant has poorly controlled hypertension \[defined as systolic blood pressure (SBP) ≥ 140 mmHg or diastolic blood pressure (DBP) ≥ 90 mmHg\]. If BP is poorly controlled at screen visit, initiation or adjustment of antihypertensive medication(s) is permitted during the run-in period prior to randomization. Prior to randomization, blood pressure must be assessed three times and the mean SBP/DBP must be \< 140/90 mmHg in order for a patient to be randomized. * Substantive renal disease (eGFR \ 1.5 x upper limit of normal. * Urine protein to creatinine ratio \> 0.4. * Neutrophil count \