Final answer:
The FDA defines a rare disease as one affecting fewer than 200,000 individuals in the U.S. This definition comes into play with the Humanitarian Device Exemption that facilitates the approval of medical devices for these rare conditions.
Step-by-step explanation:
The FDA defines a rare disease for the purposes of a Humanitarian Device Exemption as one that affects fewer than 200,000 people in the United States. This is part of their broader mission which involves medical humanitarian assistance, particularly in bringing therapies to market that address unmet medical needs. The FDA's Center for Devices and Radiological Health (CDRH) manages the approval process for medical devices, ensuring their safety, effectiveness, and quality.
When it comes to drug and therapy approval, the agency requires comprehensive data, including from clinical trials, to assess a therapy's effectiveness and its safety profile. For rare diseases that result from genetic mutations, traditional therapies may not be effective, which is where innovative treatments, like gene therapy exemplified in the ADA deficiency case, offer hope.