Understanding CLN5
Understanding CLN5, a Subtype of Batten Disease
Batten diseaseBatten disease is the common name for a broad class of rare, inherited disorders or diseases of the nervous system also known as neuronal ceroid lipofuscinoses, or NCLs. In these diseases, a defect in a specific gene triggers a cascade of problems that interferes with a cell’s ability to recycle certain molecules. The disease has several forms that share some of the same features and symptoms but vary in severity and age when symptoms first begin to appear. Each form is caused by a variant in a different gene. Although “Batten disease” originally referred specifically to the juvenile-onset form of NCL, the term Batten disease is increasingly used to describe all forms of NCL. The disease ultimately leads to shortened lifespan. is a group of rare neurodegenerative diseases, also known as neuronal ceroid lipofuscinosis (NCLs). Each NCL disease is classified by the gene that causes it. The name of each gene begins with CLN – ceroid lipofuscinosis, neuronal – followed by a unique number that indicates the subtype.
Changes in the normal function of these genes, due to pathogenic variantsA change in DNA that causes disease., lead to disruption of normal protein function. This disruption results in lysosomal dysfunction, and the accumulation of molecules in the cells throughout the body.
The symptoms, severity, onset, and progression across the subtypes vary. Both males and females may be affected. The subtypes of Batten disease can be found here.
The CLN5 subtype of Batten disease is caused by a variantA variant is a change in DNA. A variant may or may not cause disease. The following modifiers describe the variant: (i) pathogenic, (ii) likely pathogenic, (iii) uncertain significance, (iv) likely benign, or (v) benign depending on whether or not the variant causes disease. For example, a “pathogenic variant” may cause disease. The term “variant” has replaced the term “mutation.” in the CLN5 gene, which leads to disruption of normal CLN5 protein function. The exact function of this protein is unknown. Initial signs and symptoms of CLN5 most commonly develop in early childhood, although the precise timing may vary. The most common early signs include cognitive decline, clumsiness or challenges with movement. Another early sign is the loss of previously acquired motor (movement) skills. Seizures, muscle twitches, and jerks commonly develop between the ages of 6 and 13. The disease ultimately leads to a shortened lifespan.
Sources:
History of Batten Disease
Batten disease, a common name for a rare class of diseases called neuronal ceroid lipofuscinoses (NCLs)Refers to a group of conditions that affect the nervous system. Signs and symptoms vary widely between the forms but generally include a combination of dementia, vision loss, and epilepsy., was first described in 1903 by British neurologist and pediatrician Frederick Batten.
Today, there are 13 known subtypes of Batten disease. Symptoms and disease management for each subtype of Batten disease vary, although several subtypes share similar features and symptoms. Batten disease originally referred specifically to the juvenile-onset type of NCL, but now has been used more generally to describe all types of NCLs. Batten disease affects an estimated 2-4 out of every 100,000 children in the United States.
History of CLN5 (Neuronal Ceroid Lipofuscinosis 5)
Neuronal Ceroid Lipofuscinosis 5, CLN5, was first reported in 1991. It is an inherited neurological disease that affects both motor and sensory nerves. To date, more than 85 known cases of CLN5 exist in scientific literature.
CLN5 affects children globally, across ethnicities and races, and was first diagnosed in the Finnish population.
CLN4 and CLN9 genes have still not been identified.
Sources:
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- CLN5 disease. (n.d.). Retrieved July 31, 2019, from link.
- Mole, S. E. (2017, May 29). The value of a comprehensive natural history in late infantile CLN5 disease. Retrieved July 31, 2019, from link.
- Batten Disease Fact Sheet. (2019, June 24). Retrieved July 31, 2019, from link.
- CLN5 disease. (2019, July 16). Retrieved July 31, 2019, from link.
- Frederick Eustace Batten. (n.d.). Retrieved July 31, 2019, from link.
- Batten Disease Support and Research Association. (2000). Batten Disease Neuronal Ceroid Lipofuscinosis (Publication). Retrieved August 14, 2019, from link.
- CLN1 Disease, infantile onset and others. (n.d.). Retrieved August 14, 2019, from link.
- CLN10 disease, congenital, neonatal and late infantile. (n.d.). Retrieved August 14, 2019, from link.
- CLN2 Disease, Late Infantile. (n.d.). Retrieved August 14, 2019, from link.
- CLN8 Disease, EPMR and late infantile variant. (n.d.). Retrieved August 14, 2019, from link.
- McKusick, V. A. (1997, April 28). CEROID LIPOFUSCINOSIS, NEURONAL, 6; CLN6. Retrieved August 14, 2019, from link.
- Types of Batten Disease. (n.d.). Retrieved August 14, 2019, from link.
How CLN5 Disease Affects the Body
CLN5 disease affects children both cognitively and physically. Symptoms of the disease may include:
Science Behind CLN5 Disease
The underlying cause of CLN5 disease is found in an individual’s genetic code. In humans, each cell contains 23 pairs of chromosomes for a total of 46: 23 from their mother and 23 from their father. The first 22 pairs of chromosomes are autosomesAny chromosome in a cell that is not an X or Y sex chromosome. The average person has 22 pairs of autosomes (44 autosomes in total) in each cell that define the genetic make-up, or DNA, of the being. These chromosomes store thousands of genes and they are inherited from the beings’ parents. In addition to the 22 pairs of autosomes (44 total), beings also have one pair (2 total) sex chromosomes (X and Y in a male, and X and X in a female)., and they look the same in both males and females. The 23rd pair are sex chromosomes, which are different between males and females. Females have two copies of the X chromosomes (XX) and males have one X and one Y chromosome (XY). A variant in a gene on one of the first 22 autosomes can lead to an autosomalInheritance characteristic where a gene is located on a numbered, non-sex chromosome. These are found on one of the 22 pairs of (44 total) autosomal chromosomes in a human body where DNA is stored. This is one of several ways that a trait, disorder, or disease can be passed down through families. These chromosomes are not the sex (X or Y) chromosomes. disease.
Autosomal recessive is one of several ways that a disorder or disease is passed down through families. An autosomal recessive disorder occurs when a child inherits two copies of a mutated gene, one from the mother and one from the father. The biological parents, known as carriers, each carry only one copy of the mutated gene, and usually do not show symptoms of the disease.
CLN5 disease is inherited in an autosomal recessive pattern, meaning both copies of the CLN5 gene variant (one from each parent, or carrier) must be present for the child to be diagnosed with CLN5 disease.
Healthy CLN5 Gene
A healthy CLN5 gene provides the body with instructions for building the CLN5 protein. Although the exact function of the protein is unknown, it is thought to play a role in lysosomal function. In lysosomesSpecialized vesicles within cells that digest large molecules, breaking down excess waste products of the cell with the help of enzymes. Lysosomes may also be used to destroy invading viruses and bacteria., waste is recycled or disposed of properly, resulting in normal cellular function.
CLN5 Variant
People with CLN5 disease have a variant on the CLN5 gene, located on chromosome 12. When there is a variant or mutationA mutation is any inherited genetic change. The term “mutation” is being replaced by the term “variant.” in the CLN5 gene, the body creates a non-functional CLN5 protein, resulting in lysosomal dysfunction. The lysosome, when unable to function properly, causes a toxic accumulation of material in cells throughout the body.
Although the CLN5 protein is expressed throughout the body, nerve cells seem to be the most impacted, leading to the central nervous system-related signs and symptoms seen in patients who have CLN5.
Sources:
- CLN5 gene. (2019, December 10) Retrieved December 17, 2019, from link.
- CEROID LIPOFUSCINOSIS, NEURONAL, 5; CLN5. (2016, March 15). Retrieved June 20, 2019, from link.
- CLN5 disease. (n.d.). Retrieved June 19, 2019, from link.
- CLN5 disease. (2019, June 11). Retrieved June 19, 2019, from link.
- CLN5 gene. (2016, November). Retrieved June 20, 2019, from link.
- Neuronal ceroid lipofuscinosis 5. (n.d.). Retrieved June 20, 2019, from link.
CLN5 is a subtype of Batten diseaseBatten disease is the common name for a broad class of rare, inherited disorders or diseases of the nervous system also known as neuronal ceroid lipofuscinoses, or NCLs. In these diseases, a defect in a specific gene triggers a cascade of problems that interferes with a cell’s ability to recycle certain molecules. The disease has several forms that share some of the same features and symptoms but vary in severity and age when symptoms first begin to appear. Each form is caused by a variant in a different gene. Although “Batten disease” originally referred specifically to the juvenile-onset form of NCL, the term Batten disease is increasingly used to describe all forms of NCL. The disease ultimately leads to shortened lifespan. with late infantile onset, which means that the signs and symptoms of CLN5 begin to show during childhood years. Children living with CLN5 will often experience normal development, until they reach the ages between 4 and 7 years old, when the first signs and symptoms of the disease typically appear. After disease onset occurs, the symptoms will continue to progress.
Birth Through Age 7
Children with CLN5 typically experience normal development until they reach the ages between 4-7. Initial common signs and symptoms may include:
- Cognitive difficulties
- Initial delays with learning
- Delays with motor function and movement
- Loss of motor skills that were previously acquired (developmental regressionWhen a child loses an acquired function, milestone or fails to progress beyond a prolonged plateau after a period of relatively normal development.)
I didn’t notice any initial signs and symptoms because I was unsure of what I was looking for and he kept getting misdiagnosed.
- Wendy, mother of son living with CLN5
Adolescent years
As the disease continues to progress through adolescent years, other symptoms may become apparent:
- Vision deterioration
- Progressive dementiaThe loss of cognitive functioning which includes thinking, remembering, and reasoning which result in behavioral issues that interfere with an individual’s daily life.
- Decline in language ability
- Difficulty eating
- Loss of motor function
Challenges with cognitive and motor skills may be perceived as behavioral issues such as hyperactivityA condition of being overly active., anxiety, and obsessive activities. The child’s description of vision loss associated with CLN5 may be interpreted as hallucinations by parents or caregivers.
Childhood Years
Signs and symptoms start to become most noticeable during this stage. The signs that are most commonly seen during this time may include:
- Continued learning disabilities, including struggles with concentration and memory issues
- Vision problems or impairments
- Recurrent seizures, or epilepsy
- Uncontrollable muscle jerks (myoclonusBrief, shock-like jerks or twitching of a muscle (myoclonus).)
- Motor clumsiness
- Difficulty coordinating movements
“Austin’s perception would be off. Sometimes he would run into a doorframe, or put his foot down to search before stepping down a stair. When he was on an uneven service, he would have trouble walking. Walking up and down hills, or going from sidewalk to grass, got increasingly difficult for him.”
- Wendy, mother of son living with CLN5
Signs & Symptoms Reported by Caregivers
While the signs, symptoms, and age of onset of CLN5 may vary and can progress differently in each individual, there are common signs and symptoms that are consistent across people living with CLN5. The examples below come from parents of children with CLN5.
- Progressive vision loss (reluctance to step off curbs, squinting to look at pictures, reads a book too close to face, sees things that aren’t there, especially at night)
- Cognitive delay (isn’t meeting milestones, slow to respond verbally)
- Seizures (appearing to nod off, looks like they are startled awake, twitches and tremors)
- Clumsiness and issues with gross motor function or coordination of movement (lack of agility, reluctance to run, difficulty hopping on one foot, tripping, and falling)
- Deterioration of fine motor skills (challenges with scissors, needing a fat crayon instead of a pencil, difficulty picking up small objects)
Sources:
- Neuronal ceroid lipofuscinosis 5 (n.d.). Retrieved August 16, 2019, from link.
- Batten Disease Fact Sheet. (2019, June 24). Retrieved July 31, 2019, from link.
- Batten Disease Support and Research Association CLN5 disease. (n.d.). Retrieved August 16, 2019, from link.
- Malhas, A. Study Provides More Insight into Early Signs, Progression of CLN5 Disease. (n.d.). Retrieved August 16, 2019, from link.
- CEROID LIPOFUSCINOSIS, NEURONAL, 5; CLN5. (2016, March 15). Retrieved June 20, 2019, from link.
- Simonati, A., Williams, R. E., Nardocci, N., Laine, M., Battini, R., Schulz, A., Garavaglia, B., Moro, F., Pezzini, F., & Santorelli, F.M. (2017). Phenotype and natural history of variant late infantile ceroid‐lipofuscinosis 5. Developmental Medicine & Child Neurology, 59(8): 815-821. Retrieved December 17, 2019, from link.
Obtaining a definitive genetic diagnosis is an important first step in seeking appropriate care and treatment, learning about potential research or therapies that may become available, and preparing for the future. Patients and their families should consider discussing the implications of obtaining a diagnosis of CLN5 with their physician and a genetic counselor or other specialists who are familiar with the disease management of CLN5.
If you believe your child is showing signs or symptoms of CLN5, tests are available for a physician or other healthcare professional to order to confirm a diagnosis.
Many academic and commercial laboratories offer genetic blood testing. Testing for CLN5 may not be included in standard testing panels; however, upon request, a diagnostic genetic test including an expanded exome sequencing panelThrough this diagnostic test performed by a geneticist, the exome -- a sequence of all exons of protein coding genes in the human genome -- can be captured and analyzed with the intention of identifying a disease with a genetic component. for CLN5 can confirm a diagnosis. Your physician can help you navigate the process or refer you to a geneticist.
Patient organizations also provide helpful information and resources for genetic testing. For additional information on genetic testing and to find possible sources for testing, you can refer to these Batten disease advocacy organizations.
A representative is available to help you:
A Clinician's Perspective on Diagnosis:
“CLN5 and CLN7 are two very rare forms of
Batten diseaseBatten disease is the common name for a broad class of rare, inherited disorders or diseases of the nervous system also known as neuronal ceroid lipofuscinoses, or NCLs. In these diseases, a defect in a specific gene triggers a cascade of problems that interferes with a cell’s ability to recycle certain molecules. The disease has several forms that share some of the same features and symptoms but vary in severity and age when symptoms first begin to appear. Each form is caused by a variant in a different gene. Although “Batten disease” originally referred specifically to the juvenile-onset form of NCL, the term Batten disease is increasingly used to describe all forms of NCL. The disease ultimately leads to shortened lifespan., both marked by regression of motor and language skills, as well as seizures, during childhood years. While signs and symptoms for both are similar to other types of Batten disease, these subtypes are not currently tested within a standard panel. If your child is experiencing motor and language regression, consider speaking to your healthcare provider about an expanded exome sequencing panelThrough this diagnostic test performed by a geneticist, the exome — a sequence of all exons of protein coding genes in the human genome — can be captured and analyzed with the intention of identifying a disease with a genetic component.. With a positive diagnosis, children may be eligible to participate in research that could help the community better understand Batten disease.”
Elizabeth Berry-Kravis, M.D., Ph.D.,
Pediatric Neurologist and Professor
Rush University Medical Center
While there is currently no cure for children living with CLN5, there are a number of specialists with expertise who can help families affected by CLN5 manage their disease and its symptoms.
Children living with CLN5 benefit from having a team of healthcare professionals and assistive devices to help manage the progressive impact of their disease. The daily needs of an individual with CLN5 can be supported by some or all the following healthcare providers. These needs may evolve as the child moves into adulthood or as the disease progresses.
Click on each circle below for more information about the role each healthcare provider may play to support the daily needs of an individual living with CLN5:
In addition to the care team that can help to manage the various symptoms associated with CLN5 disease, people caring for a child with CLN5 disease may also find support through social and educational plans. These plans support the family as symptoms progress.
Sources:
- Batten DiseaseBatten disease is the common name for a broad class of rare, inherited disorders or diseases of the nervous system also known as neuronal ceroid lipofuscinoses, or NCLs. In these diseases, a defect in a specific gene triggers a cascade of problems that interferes with a cell’s ability to recycle certain molecules. The disease has several forms that share some of the same features and symptoms but vary in severity and age when symptoms first begin to appear. Each form is caused by a variant in a different gene. Although “Batten disease” originally referred specifically to the juvenile-onset form of NCL, the term Batten disease is increasingly used to describe all forms of NCL. The disease ultimately leads to shortened lifespan. Fact Sheet. (2019, May 14). Retrieved June 19, 2019, from link.
- CLN5 disease. (n.d.). Retrieved June 19, 2019, from link.
- CLN5 disease. (2019, June 11). Retrieved June 19, 2019, from link.
