Mondo Description Neuronal ceroid lipofuscinosis 9 (CLN9-NCL) is a rare condition that affects the nervous system. Signs and symptoms of the condition generally develop in early childhood (average age 4 years) and may include loss of muscle coordination (ataxia), seizures that do not respond to medications, muscle twitches (myoclonus), visual impairment, and developmental regression (the loss of previously acquired skills). The underlying genetic cause of CLN9-NCLis unknown but it appears to be inherited in an autosomal recessive manner. Treatment options are limited to therapies that can help relieve some of the symptoms.