A global, multi-center, Disease Monitoring Study (DMS) in participants with Autosomal Dominant Hypocalcemia Type 1 (ADH1) or Autosomal Dominant Hypocalcemia Type 2 (ADH2) designed to characterize ADH1 and ADH2 disease presentation and progression through retrospective (past) and longitudinal prospective (over time into the future) data collection.

The ADH1 and ADH2 DMS is designed to better understand the disease burden of ADH1 and ADH2, how participants with ADH1 or ADH2 are managed with standard of care practices in a real-world setting, and how standard of care treatment impacts ADH1 and ADH2 symptoms.

The study will include adult and pediatric participants with a confirmed clinical diagnosis of ADH1 or ADH2. Each participant's data will be collected over a period of up to 5 years. In addition, retrospective (or past) data will be collected.

Key Inclusion Criteria:

• Have a documented activating variant or variant of uncertain significance of the CASR gene causative of ADH1 or documented activating variant or variant of uncertain significance of the GNA11 gene causative of ADH2 associated with a clinical syndrome of hypoparathyroidism prior to enrollment

Note: Acceptable documentation includes CASR or GNA11 genetic analysis report. If no prior documented CASR or GNA11 gene variant or variant of uncertain significance, potential participants can undergo CASR and GNA11 gene variant analysis at Screening.

• Be willing and able to provide informed consent or assent after the nature of the study and its details have been explained, and prior to any research-related procedures
• Be willing and able to provide access to prior medical records including imaging, biochemical, and diagnostic and medical history data, if available
• Be willing and able to comply with the study visit schedule and study procedures

Key Exclusion Criteria:

• Have serious medical or psychiatric comorbidity that, in the opinion of the Investigator, would present a concern for participant safety or compromise the ability to provide consent or assent, or comply with the study visit schedule and study procedures
• Enrollment in an interventional clinical study at the time of DMS Screening visit

Note: Other protocol defined Inclusion/Exclusion criteria may apply.

Eligible participants include children (birth to 17 years) and adults (18 - 90 years) with ADH1 or ADH2 as determined by an activating variant of CASR in ADH1 or GNA11 in ADH2.