Rare and ultra-rare diseases, often referred to as orphan and ultra-orphan diseases, affect very small numbers of patients.
Patients with NALCN gene mutation have an ultra-rare genetic disease.
In the United States, a disease is defined as rare if it affects fewer than 200,000 people (or, approximately 620 patients per million of population).
The European definition of a rare disease is one that affects fewer than five people per 10,000 of the population (or, approximately 500 patients per million of population).
In contrast, a disease is generally considered to be ultra-rare if it affects one patient per 50,000 people (or, fewer than 20 patients per million of population)—and most ultra-rare diseases affect far fewer than this—as few as one per million or less.
Despite the very small number of patients they affect, the impact that ultra-rare diseases have on patients, their families, and society is profound, as many are severe, chronic and progressive. Patients with severe and life-threatening ultra-rare diseases often live without hope as they have no effective treatment options.