CLN1 disease

CLN1 disease is an inherited disorder that primarily affects the nervous system. Individuals with this condition have normal development in infancy, but typically by 18 months they become increasingly irritable and begin to lose previously acquired skills (developmental regression). In affected children, nerve cells in the brain die over time, leading to an overall loss of brain tissue (brain atrophy) and an unusually small head (microcephaly). Children with CLN1 disease have decreased muscle tone (hypotonia), intellectual and motor disability, and rarely are able to speak or walk. Some affected children develop repetitive hand movements. By age 2, individuals with this condition often have muscle twitches (myoclonus), recurrent seizures (epilepsy), and vision loss. Some affected children develop frequent respiratory infections. As the condition worsens, children have severe feeding difficulties that often require a feeding tube. Children with CLN1 disease usually do not survive past childhood.

Some people with CLN1 disease do not develop symptoms until later in childhood or in adulthood. As with younger affected children, older individuals develop a decline in intellectual function, myoclonus, epilepsy, and vision loss. In these individuals, life expectancy depends on when signs and symptoms of CLN1 disease develop and their severity; affected individuals may survive only into adolescence or through adulthood. Adults with CLN1 disease may also have movement disorders, including impaired muscle coordination (ataxia) or a pattern of movement abnormalities known as parkinsonism.

CLN1 disease is one of a group of disorders known as neuronal ceroid lipofuscinoses (NCLs), which may also be collectively referred to as Batten disease. All these disorders affect the nervous system and typically cause worsening problems with vision, movement, and thinking ability. The different NCLs are distinguished by their genetic cause. Each disease type is given the designation "CLN," meaning ceroid lipofuscinosis, neuronal, and then a number to indicate its subtype.