What Is CLN8-Related Neuronal Ceroid Lipofuscinosis?
CLN8-related neuronal ceroid lipofuscinosis (NCL8) is an inherited condition that causes degeneration of the brain, leading to a progressive loss of mental and motor skills, seizures, and vision impairment in some cases. There are several forms of neuronal ceroid lipofuscinosis (NCL), largely differentiated by the gene responsible and the age at which symptoms begin. Mutations in the CLN8 gene typically result in variant late-infantile neuronal ceroid lipofuscinosis (vLINCL) or Northern epilepsy (also know as Progressive Epilepsy with Mental Retardation, or EPMR). Northern epilepsy accounts for almost 100% of NCL8 cases in Finland but is generally rare.
Variant late-infantile neuronal ceroid lipofuscinosis The symptoms of vLINCL typically begin between 3 and 8 years of age. Early symptoms include epilepsy, vision loss, and difficulty controlling movements. Over time, motor and intellectual skills decline and epilepsy and vision loss worsens. Death occurs in late childhood or in adolescence.
Northern epilepsy Symptoms of Northern epilepsy typically begin between 5 and 10 years of age. Typical symptoms include recurrent seizures and a slow decline in mental function. The frequency of seizures decreases after puberty, and vision problems are rare. Individuals with Northern epilepsy live into late adulthood, with some living beyond age 60.
How Common Is CLN8-Related Neuronal Ceroid Lipofuscinosis?
The worldwide prevalence of NCL (all forms) is approximately 1 in 100,000. These diseases are most common in Scandinavian countries but occur elsewhere as well. Northern epilepsy occurs primarily in the Kainuu region of northern Finland, where the prevalence of the condition is approximately 1 in 10,000. The exact proportion of NCL cases that are caused by mutations in the CLN8 gene is currently unknown.
How Is CLN8-Related Neuronal Ceroid Lipofuscinosis Treated?
There is no treatment for the underlying cause of NCL8. Seizures may be controlled with medication. However, not all individuals with NCL8 will respond to anti-seizure medications, and treatment will not slow the progression of the disease. Additional treatments address symptoms of the condition as they arise, such as medications for the various movement problems.
What Is the Prognosis for an Individual with CLN8-Related Neuronal Ceroid Lipofuscinosis?
Individuals with severe vLINCL survive into late childhood or adolescence. Individuals with Northern epilepsy often live until the fifth or sixth decade of life. However, these individuals have significant cognitive and physical impairments for much of their lives. While vision impairment may occur, significant vision loss is not as common with NCL8 as it is with other types of NCL.