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Batten disease (CLN5, late infantile variant)
This type of Batten disease often presents in late infancy with developmental regression, seizures, and vision loss. It is caused by genetic changes in the CLN5 gene and is passed down in an autosomal recessive manner.
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Overview
Batten disease, specifically the CLN5 late infantile variant, is a progressive and severe neurological condition. It belongs to a group of disorders known as neuronal ceroid lipofuscinoses (NCLs) [PMID:33678096]. These conditions are characterised by the accumulation of fatty substances (lipofuscins) within cells, particularly neurons in the brain, leading to cell damage and impaired function. The CLN5 variant typically manifests in late infancy or early childhood, causing a decline in previously acquired skills.
Over time, affected individuals experience worsening neurological symptoms. The condition is very rare, though its exact prevalence in the UK population is not well established. It is more commonly observed in the Finnish population due to a founder effect [PMID:15334460].
Symptoms & clinical features
The symptoms of CLN5 Batten disease generally begin between 2 and 7 years of age. Initial signs may include a slowdown or regression in development, where a child starts losing skills they had previously learned, such as speaking or walking. Early symptoms often involve speech difficulties and problems with coordination.
As the condition progresses, affected children typically develop seizures that can be difficult to control. Vision loss is another prominent feature, which can lead to complete blindness. Movement problems, including difficulties with balance and walking, become more severe. In later stages, profound intellectual disability also develops, and communication skills diminish significantly [PMID:14681682].
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Affected organs
Batten disease primarily affects the nervous system. The brain is extensively impacted, leading to the various neurological symptoms observed, such as developmental regression, seizures, and cognitive decline. The retina, which is the light-sensitive tissue at the back of the eye, is also significantly affected, causing progressive vision loss.
While the main impact is on the brain and eyes, these lysosomal storage disorders affect cells throughout the body because of the widespread nature of lysosomes. However, the most pronounced and debilitating effects are on neuronal tissues.
Risks & severity
The CLN5 late infantile variant of Batten disease is a severe, progressive condition. It leads to a gradual and irreversible decline in neurological function. There is considerable variability in the precise age of symptom onset, which generally ranges from 2 to 7 years. The progression of the disease varies among individuals, but it typically results in significant disability and reduced life expectancy.
There is currently no cure for Batten disease; management focuses on supportive care to address symptoms and improve quality of life. The severity and progressive nature of the condition mean that affected children will require increasingly intensive medical and care support throughout their lives.
Genetic causes
Batten disease (CLN5, late infantile variant) is caused by pathogenic changes (sometimes called mutations) in the CLN5 gene, located on chromosome 13. The CLN5 gene provides instructions for making a protein that is thought to be involved in the function of lysosomes. Lysosomes are vital compartments within cells responsible for breaking down and recycling waste products.
When the CLN5 protein is not working correctly due to a pathogenic variant, waste materials, particularly a substance called lipopigment (neurolipofuscin), accumulate within cells. This accumulation is toxic to cells, especially neurons, leading to their damage and death. The result is the progressive neurological degeneration seen in Batten disease.
- CLN5 CLN5 lysosomal BMP synthaseThe CLN5 gene provides instructions for a protein important for lysosomal function, and variants in CLN5 are associated with a form of Batten disease.
Inheritance pattern
CLN5 Batten disease is inherited in an autosomal recessive manner. This means that an individual must inherit two copies of the altered CLN5 gene - one from each parent - to develop the condition.
Parents who each carry one altered copy of the CLN5 gene are known as carriers. Carriers typically do not show any symptoms of the disease themselves because they have one working copy of the gene. For each child born to two carrier parents, there is a 25% chance of inheriting both altered copies and developing the condition, a 50% chance of inheriting one altered copy and being a carrier, and a 25% chance of inheriting two normal copies and not being affected or a carrier.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
Diagnosis & testing
Diagnosing CLN5 Batten disease typically begins when a child presents with the characteristic symptoms of developmental regression, seizures, and vision problems. A paediatric or neurology specialist will evaluate the child's clinical presentation.
Confirmation of the diagnosis is made through genetic testing. This testing involves analysing a sample of blood or saliva to identify pathogenic variants within the CLN5 gene. In the UK, such testing is available through the NHS Genomic Medicine Service (GMS). Referral for genetic testing, often following initial clinical suspicion, can be made by a specialist paediatrician or neurologist. The relevant NHS Genomic Medicine Service 'R-code' for general NCL disorders, which would include CLN5, is R66. Genetic counselling is an important part of the diagnostic process, providing information and support to families.
Management & lifestyle
Currently, there is no cure for CLN5 Batten disease, and management focuses on providing supportive care to alleviate symptoms and improve the quality of life for affected individuals. A multidisciplinary team, including neurologists, ophthalmologists, physiotherapists, occupational therapists, speech and language therapists, and palliative care specialists, is often involved.
Treatment approaches include medications to help control seizures and manage other neurological symptoms. Therapies such as physiotherapy and occupational therapy can help maintain mobility and functional skills for as long as possible. Special educational support and visual aids are also important given the progressive developmental regression and vision loss. Regular follow-up appointments with specialists within the NHS framework are crucial to monitor disease progression and adjust supportive care as needed.
UK care pathway
In the UK, individuals suspected of having genetic conditions like Batten disease (CLN5, late infantile variant) can be referred into the NHS Genomic Medicine Service (GMS) pathway. This pathway enables access to specialist diagnostic services, including genomic testing under a relevant 'R-code' (e.g., R66 for NCL disorders). Referrals typically come from a specialist children's doctor (paediatrician) or a neurologist. Following a diagnosis, patients and their families are often supported by clinical genetics services, which include access to genetic counsellors. Genetic counsellors provide essential information about the condition, its inheritance, and implications for the wider family, as well as offering emotional support.
Frequently asked questions
What is the typical age of onset for CLN5 Batten disease?
Symptoms of CLN5 Batten disease generally begin in late infancy or early childhood, typically between the ages of 2 and 7 years. The initial signs often include developmental regression and speech difficulties.
Is there a cure for CLN5 Batten disease?
Currently, there is no cure for CLN5 Batten disease. Management focuses on supportive care, which aims to alleviate symptoms, maximise comfort, and improve the quality of life for affected individuals through a multidisciplinary approach.
How is CLN5 Batten disease inherited?
CLN5 Batten disease is inherited in an autosomal recessive pattern. This means an individual must inherit two copies of the altered CLN5 gene, one from each parent, to develop the condition. Parents who each carry one altered gene copy are usually unaffected carriers.
Can genetic testing help confirm a diagnosis?
Yes, genetic testing is the definitive way to confirm a diagnosis of CLN5 Batten disease. This test identifies pathogenic variants in the CLN5 gene and is typically arranged through specialist services within the NHS Genomic Medicine Service.
What kind of doctors treat Batten disease?
Care for Batten disease typically involves a team of specialists, including paediatric neurologists, ophthalmologists, physiotherapists, occupational therapists, and speech and language therapists. Genetic counsellors also provide crucial support to families.