Rare Genetic Disorders

In the United States, a rare disease is defined as a condition that affects fewer than 200,000 people in the US.  There may be as many as 7,000 rare diseases. The total number of Americans living with a rare disease is estimated at between 25-30 million. There are many different causes of rare diseases. The majority are thought to be genetic, directly caused by changes in genes or chromosomes. In some cases, genetic changes that causes disease are passed from one generation to the next.