SNP Shot: Genomic Insights

CLN8 disease is a genetic condition impacting the nervous system, with symptoms and life expectancy varying among affected individuals. The disease is broadly categorized into less-severe and more-severe forms, distinguished by the specific symptoms that manifest and how long a person lives.

The less-severe type of CLN8 disease, sometimes called Northern epilepsy, is marked by recurring seizures (epilepsy) and a decrease in cognitive abilities that starts between 5 and 10 years of age. These seizures may be difficult to control with medication and are often generalized tonic-clonic seizures, characterized by muscle stiffness, convulsions, and loss of consciousness. Some individuals also experience partial seizures, which do not involve loss of consciousness. Seizure frequency is typically one to two times a month until adolescence, decreasing to four to six times a year in early adulthood. By middle age, seizures become even rarer. In addition to seizures, individuals experience a gradual decline in thinking skills and develop problems with coordination and balance. Vision problems can emerge in early to mid-adulthood. People with the less-severe form of CLN8 disease often live into their late adult years.

The more-severe type of CLN8 disease usually appears between the ages of 2 and 7. Seizures in this form involve involuntary muscle jerks (myoclonic epilepsy). Individuals with this type show a more significant decline in intellectual function and often lose the ability to speak. Vision loss is also a common symptom. These individuals have increasing difficulty with walking and coordination (ataxia), eventually becoming immobile. Those with the more-severe form of CLN8 disease typically survive only into late childhood or adolescence.

CLN8 disease belongs to a group of disorders known as neuronal ceroid lipofuscinoses (NCLs), also referred to as Batten disease. These disorders affect the nervous system, leading to worsening vision, movement difficulties, and cognitive impairment. The different NCLs are classified by their underlying genetic cause and are designated "CLN," followed by a number indicating the specific subtype.

Inheritance:

This condition follows an autosomal recessive inheritance pattern. This means that an individual must inherit two copies of the mutated gene (one from each parent) to develop the disease. Parents who each carry one copy of the mutated gene are typically asymptomatic carriers.