This dose range of 0.7-1mg/kg/day was chosen for LM patients as it was the low end of dose range for infants treated with propranolol for problematic hemangiomas, a related vascular anomaly. At this dose, no significant hemodynamic adverse effects were noted in LM patients. However, when patients stopped propranolol or their dose fell below 0.7mg/kg/day, they suffered rebound worsening of their symptoms. Moreover, inflammatory events such as infections temporarily overcame the effects of 0.7-1mg/kg/day of propranolol. Thus, it is unknown whether maximum propranolol efficacy was achieved at the current dose range. The investigators propose to examine whether optimized propranolol usage for treatment of LM patients has been achieved. The primary endpoint for this study is to ascertain whether LM patients can tolerate higher doses of propranolol, as measured by known propranolol adverse effects and patient-reported symptoms. A secondary endpoint will address whether patient-reported LM symptoms and quality of life are improved with higher doses of propranolol; objective findings such as LM size on physical examination and imaging studies will be analyzed as well. In addition, LM tissue biopsies will acquired from patients before and after propranolol treatment for further analyses of disease progression.