A rare disease is a health condition that affects a small percentage of the population, typically defined as fewer than 200,000 people in the United States. These diseases can be genetic, infectious, or autoimmune, and often have limited treatment options due to their low prevalence. Many rare diseases are not well understood, leading to challenges in diagnosis and management. Patients may face difficulties in finding specialists or support networks, as awareness and research funding for these conditions are often limited. Organizations like the National Organization for Rare Disorders work to improve understanding and support for those affected.