Batten disease and other forms of NCL are relatively rare, occurring in an estimated 4 of every 100,000 births in the United States. These disorders appear to be more common in Finland, Sweden, other parts of northern Europe, and Newfoundland, Canada. The incidence in Australia is not known precisely. Although NCLs are relatively rare, they can often strike more than one person in families that carry the defective gene. A family can be affected by one type of NCL only.