Adult Batten disease is a very rare subtype of Batten disease (also known as neuronal ceroid lipofuscinosis, NCL), whose symptoms usually appear when patients reach their 30s. But this form’s onset ranges from adolescence to over age 50.
Adult Batten disease is sometimes called Kufs disease.
It tends to run a milder course than the more common childhood forms of Batten disease. Vision is usually preserved, and life expectancy is not shortened.
Causes of Batten disease
In all forms of Batten disease, there is a build-up of a fatty pigment called lipofuscin in lysosomes. Lysosomes are 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 disease, they suspect that all of them affect lipofuscin processing.
Types of adult Batten disease
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 PPT1 or the CLN6 gene. People with mutations in the PPT1 gene may also be referred to as having CLN1 disease. PPT1 gene defects lead to a lack 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 more severe gene defects 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.
Mutations in the CLN6 gene are thought to lead to problems in protein transport and processing. As with CLN1 disease, milder mutations in the CLN6 gene result in adult Batten disease, while more serious mutations may cause patients to develop Batten disease in childhood.
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 abnormal CSPα, a protein that helps recycle other proteins and that is critical in allowing information to be passed from one nerve cell to the other.
Autosomal recessive means that patients must have two copies of the defective gene – one inherited from each parent – for disease symptoms to develop. Autosomal dominant means that only one copy of the defective gene, which can be inherited from either parent, is disease-causing.
Patients with type A adult Batten disease usually experience progressive myoclonic epilepsy, a condition that involves seizures accompanied by uncontrollable jerky movements called myoclonus. Patients can also develop other involuntary movements, such as tics or tremors, poor coordination (ataxia), 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. But behavioral abnormalities, and possibly dementia, mark this adult form.
Diagnosis of adult Batten disease
A combination of genetic tests to confirm the presence of gene defects, measurements of certain enzyme levels, as well as a skin biopsy to look for the characteristic lipofuscin deposits may be needed to diagnose adult Batten disease.
Treatment and management
Treatments available are not able to cure Batten disease. Instead, they aim at improving its symptoms and patients’ quality of life. Examples of treatments include anticonvulsants to control seizures, and physical and occupational therapy. Genetic counseling and psychosocial support may also be helpful for people affected by adult Batten disease.
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