Definition:
Northern Epilepsy/variant late infantile CLN8 disease is part of a group of progressive degenerative neurometabolic disorders known as neuronal ceroid lipofuscinoses (NCLs). NCLs are characterized by an abnormal accumulation of lipopigaments; subtances combined of fats and proteins within the brain’s nerve cells, eyes, skin, muscle, and within other tissues throughout the body.

Although this disorder has clinical symptoms similar to other NCLs, it is distinct because its cause is known. The cause of many NCLs remains nebulous. Northern Epilepsy/variant late infantile CLN8 disorder is caused by a mutation on the CLN8 gene. The mutation results in an accumulation of transmembrane proteins in the cells. The gene CLN8 provides the code for a specific transmembrane protein, but its exact function is unknown. This mutation essentially eliminates the function of the CLN8 gene and gives rise to the symptoms of this disorder. Five mutations on the CLN8 gene have been identified. This disorder causes nerve cells, found in the brain, retina, and in the central nervous system, to die.

Northern Epilepsy/variant late infantile CLN8 has been found only in the Finnish population and its exact frequency is not known. It is therefore considered a unique clinical and genetic disorder among other NCLs.

It is estimated that the NCLs affect two to four of every 100,000 live births in the United States.

Symptoms:
Early development is normal for children affected by Northern Epilepsy/variant late infantile CLN8. Seizures begin to appear between the ages of five and 10 in affected children followed by progressive mental retardation. Decreased vision and slight motor skills problems are also symptoms.

Inheritance Pattern:
Northern Epilepsy/variant late infantile CLN8 is an autosomal recessive disorder.

Life Expectancy:
Life Expectancy for Northern Epilepsy/variant late infantile CLN8 is 50 years of age.

Diagnosis and Testing:
A DNA analysis may be utilized to diagnose Northern Epilepsy/variant late infantile CLN8. This analysis would be utilized to confirm a mutation on the CLN8 gene. Blood or a tissue sample is tested from individuals who are suspected of having the disorder or from family members wherein a carrier of the CLN8 gene has been identified. Prenatal screening is also available.

Treatment:
There is no cure for Northern Epilepsy/variant late infantile CLN8. Treatment is limited to reducing or controlling the symptoms of this disorder by consulting regularly with neurologists, ophthalmologists and genetic counselors. Neurologists assist in keeping seizures or nervous system complications under control. An ophthalmologist monitors vision loss, and physical and occupational therapists can assist the affected individual to maintain muscle movement and reduce muscle discomfort. Medication can control seizures that are characteristic to this disorder.