Inclusion Criteria:  Adult persons with Menkes disease who survived beyond the expected natural history, attained independent ambulation, attend (or attended) school, and reached adulthood after early CuHis treatment for three years or adults with Occipital Horn Syndrome, who manifest clinical signs and symptoms of dysautonomia, e.g., orthostatic hypotension: specifically, a decrease in systolic or diastolic blood pressure of at least 20 or 10 mm Hg, respectively, within three minutes after standing, and/or chronic diarrhea: production of loose stools with or without increased stool frequency for more than four weeks immediately preceding enrollment. History of at least thrice weekly occurrence of dizziness/feeling lightheaded while standing upright and/or thrice weekly episodes of diarrhea or an urgent need to defecate after food ingestion for more than four weeks immediately preceding enrollment. Documented mutation in ATP7A. Must sign and date an Informed Consent Form (ICF). Age ≥ 18 years of age. Ability to adhere to the prescribed oral Northera (Droxidopa) regimen. Willingness to comply with all study visits and procedures.  Exclusion Criteria:  Pre-existing liver (e.g., hepatitis, biliary atresia, cirrhosis) or kidney disease (i.e., calculated glomerular filtration rate <30 ml/min). History of hypertension, anti-hypertensive therapy, heart failure (or decreased ejection fraction), cardiac arrhythmia, or bleeding diatheses. Any disease or condition that, in the opinion of the Investigator, has a high probability of precluding the subject from completing the study or where the subject cannot or will not appropriately comply with study requirements. Any alpha-1 adrenoreceptor agonist, beta-blocker, DOPA decarboxylase inhibitor, midodrine, ephedrine, or any triptan medication as a concomitant medication.