Natural History of Patients With PH3 and a History of Stone Events

The relationship between the level of Uox and the incidence of kidney stones and/or nephrocalcinosis in patients with PH3 has not been established. The goal of this study is to record 24-hour Uox levels and the incidence of new stone formation and/or the degree of nephrocalcinosis in patients with PH3 over time. Potential participants are screened over an up-to-7 week period according to the eligibility criteria and will then be followed every 6 months over an up-to-2-year period to determine the annualized new stone formation rate (number of new stones being formed per year) and the change in the degree of nephrocalcinosis (if applicable). New stone formation is defined as occurrence of any of the following: * Spontaneous stone passage in the absence of pre-existing stones * Stone passage occurring without change in the number of pre-existing stones detected by renal ultrasound * Appearance of new stones on renal ultrasound or 100% or more growth of a pre-existing stone (estimated area) * Surgical removal of newly formed stones Note: Spontaneous passage or surgical removal of pre-existing stones does not meet the criteria for new stone formation. This is a non-interventional study that will last up to 2 years.