Adult Batten disease is a very rare subtype of Batten disease, in which symptoms don’t usually appear until patients reach their 30s.
While the symptoms of most types of Batten disease, also known as neuronal ceroid lipofuscinosis or NCL, occur at birth or during childhood, this form’s age of onset can range from 25 to 50.
This subtype is sometimes called Kufs disease. It is estimated to affect about 1.5 people per 9 million in the general population at any given time.
Adult Batten tends to run a milder course than the more common childhood forms of Batten disease and vision is usually preserved. But adults with this disorder — caused by mutations in different genes — often experience muscle contractions and seizures, and sometimes movement and coordination problems.
Causes
In all forms of Batten disease, there is a buildup of a fatty residue called lipofuscin in lysosomes, which are the parts of the cell where waste disposal occurs. Brains cells are particularly sensitive to the harmful effects of lipofuscin accumulation, leading to the neurological symptoms experienced by Batten patients.
A total of 14 mutated genes are known to be associated with different forms of Batten disease. While scientists do not fully understand how mutations in these genes lead to Batten, they suspect that all of them affect lipofuscin processing.
There are two major types of adult Batten disease, type A and type B. Each is caused by mutations in different genes.
Type A adult Batten disease results from mutations in either the CLN6 or the CLN1 gene.
Mutations in the CLN6 gene are thought to lead to problems in protein transport and processing. Milder mutations in the CLN6 gene result in adult Batten disease, while more serious mutations may cause patients to develop Batten in childhood.
CLN1 gene defects lead to reduced levels of the PPT1 enzyme, which normally breaks down lipids in cells. Different genetic mutations have varying effects on the levels of PPT1 enzyme activity, which in turn affects the age of symptom onset. Those with mutations that lead to very little or no PPT1 enzyme activity usually go on to develop infantile Batten disease, while those with milder mutations develop adult Batten disease.
Type B adult Batten disease is caused by mutations in either the CTSF gene (CLN13 disease) or the DNAJC5 gene (CLN4 disease).
CTSF gene defects cause problems in the production of an enzyme called cathepsin F, which is thought to be involved in facilitating lysosome function. DNAJC5 defects lead to the production of altered CSPalpha, a protein that helps recycle other proteins and that is critical in allowing information to be passed from one nerve cell to the other.
Mutations in other genes, including CLN5, CLN3, CTSD, GRN, and MFSD8 also have been associated with the adult form of Batten disease.
Inheritance
While type A adult Batten disease is inherited in an autosomal recessive manner, type B disease is inherited in an autosomal dominant manner.
Autosomal recessive means that individuals must inherit two copies of the defective gene — one from each parent — to develop the disease. Autosomal dominant means that only one copy of the defective gene, which can be inherited from either parent, is necessary for the individual to develop the disorder.
Symptoms
Patients with type A adult Batten disease usually experience progressive myoclonic epilepsy, a condition that involves seizures accompanied by muscle contractions (myoclonus). Individuals can also develop other involuntary movements, such as tics or tremors, poor coordination (ataxia), dementia, and difficulty speaking (dysarthria).
Those with type B adult Batten disease often experience many features of type A disease. However, they are less likely to develop speaking problems or myoclonic seizures. Behavioral abnormalities, and possibly dementia, do mark the type B form of adult Batten.
Treatment and management
There currently are no effective treatment options for adult-onset Batten disease. Available therapies seek to lessen the disease symptoms and improve patients’ quality of life. Examples of treatments include anticonvulsants to control seizures, and physical and occupational therapy. Genetic counseling and psychosocial support also may be helpful for people affected by adult Batten disease.
Last updated: Oct. 11, 2021
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