Study 200195 App’s purpose is to support GSK Study 200195 (Adenosine Deaminase Severe Combined Immunodeficiency (ADA-SCID) Registry for Patients Treated with Strimvelis™ (or GSK269273) Gene Therapy: Long-Term Prospective, Non-Interventional Follow-up of Safety and Effectiveness). Registry participant’s will be able to use the app to enter the required information for the study.