How Prevalent is CLS in the population?

In the United States, about 1 per 14,285 people, or 19,040 individuals are affected by CLS. This is about 0.01% of Americans who have CLS. The National Institute of Health Office of Rare Diseases Research defines a rare disease as affecting less than 20,000 people in the United States. Coffin-Lowry Syndrome fits that description and is on their list of rare diseases which can be found here.