Rare diseases represent a wide range of disorders and constellations of clinical signs and symptoms. Many rare diseases cause chronic or progressive physical deterioration, disability, or premature death and start in childhood, creating a huge burden on parents and caregivers. Most rare diseases are thought to be genetic and there may be as many as 7000 rare diseases [1]. Although there is no universally accepted terminology or definition as to what constitutes a rare disease, it is typically characterized by its low frequency of occurrence.
