Defining Batten Disease
Batten disease is a form of fatal inherited disorder that affects a person's nervous system. Batten disease starts during childhood and in some cases the signs are rather subtle, taking on the form of behavioral and personality changes, as well as clumsiness, slow learning, or stumbling. The symptoms presented by Batten disease are connected to a buildup of substances known as, 'lipopigments,' in the person's bodily tissues. Lipopigments are comprised of fats and proteins. Vision loss is an early sign of Batten disease and can be an indicator that is caught during an eye examination. Many times, an optometrist or doctor might refer a child to a neurologist. Diagnostic testing for Batten disease includes urine or blood testing, tissue or skin sampling, an EEG, brain scans, and electrical studies of the person's eyes.
The early symptoms of the disease can appear between the ages of five and ten. Parents or a doctor might notice that a child has started to develop vision issues, or seizures. Over time, children with Batten disease experience worsening seizures, mental impairment, as well as progressive loss of their motor skills and vision. At some point, children with the disease become blind, stay in bed, and experience dementia. People affected by Batten disease often die by the time they reach late adolescence or their twenties.
Batten disease is named after the British pediatrician who described it in the year 1903. The disease is also known as, 'Spielmeyer-Vogt-Sjogren-Batten disease,' and is the most common form of a group of disorder referred to as, 'neuronal ceroid lipofuscinoses,' or NCL's. While Batten disease is commonly regarded as the juvenile form of NCL, there are some doctors who use the term, 'Batten disease,' in order to describe any form of NCL.
Batten disease, as well as other forms of NCL's, are fairly rare. They happen in approximately two to four out of every one-hundred thousand persons born in America. The disorders seem to be more common in nations such as Sweden, Finland, and other parts of northern Europe, as well as Newfoundland, Canada. Despite being classified as rare diseases, NCL's many times affect more than one person in families who carry the defective genes. There are an estimated several hundred children in America that have Batten disease.
Batten disease is a form of autosomal recessive disorder, meaning that it only happens when a child inherits two copies of the defective gene - one from each of their parents. When both of the child's parents carry one defective gene, each of their children has a twenty-five percent chance of developing Batten disease. Each child also has a fifty-percent chance of inheriting just one copy of the defective gene. People who have one defective gene are referred to as, 'carriers,' meaning that they do not develop Batten disease, yet have the ability to pass the gene to their own children.
Causes of Batten Disease
The symptoms of Batten disease, as well as other forms of NCL's, are linked to a buildup of substances referred to as 'lipofuscins,' or, 'lipopigments,' in the person's body tissues. Lipopigments are made up of proteins and fats. Lipopigments build up inside the person's brain cells, optic nerve, skin, muscles, and other tissues. The pigments create deposits with distinctive shapes that can be viewed under an electron microscope. Some appear similar to half-moons, while others look like fingerprints. Average human systems consistently dispose of lipofuscins. People with Batten disease have genes that prevent their body from doing so.
Medical science has discovered the biochemical defects that underlie several NCL's. There is an enzyme called, 'palmitoyl-protein thioestarase,' that has been demonstrated to be insufficiently active in the infantile form of Batten disease, a condition that is now referred to as, 'CLN1.' There is a late infantile form referred to as, 'CLN2,' where a deficiency of an acid protease - an enzyme which hydrolyzes proteins, has been discovered as the cause of the condition. A gene mutation has been identified in juvenile Batten disease, referred to as, 'CLN3,' as well as a protein related to is referred to by the same reference. There have been forty-two mutations discovered in association with CLN3. One of the mutations in which some of the gene is missing is responsible for eighty-five percent of the people with juvenile NCL of European descent.
Diagnosing Batten Disease
Obtaining an accurate diagnosis can be difficult because Batten disease is rare; many doctors are unfamiliar with the disease. Because of this a misdiagnosis is common, leading to frustration on the part of family members. As mentioned, vision loss is many times an early sign of the disease, so it may be first suspected by a professional performing an eye examination. An eye doctor has the ability to detect a loss of cells within a person's eye that happens during the three childhood forms of NCL. Unfortunately, because the kind of cell loss that happens in other eye diseases, Batten disease is something that cannot be diagnosed by this sign alone. Many times an eye doctor or physician who suspects Batten disease will refer the child to a neurologist who specializes in brain and nervous system diseases.
Modern genetic testing, as well as blood testing, may confirm Batten disease. There are a number of additional diagnostic tests that can be performed.
Blood or urine tests: Blood or urine tests may detect abnormalities which can indicate the disease. Elevated levels of dolichol, for example, may be found in the urine of persons with NCL's.
Skin or tissue sampling: A doctor can examine a sample of the person's tissue underneath an electron microscope for NCL deposits, which are common in skin cells; particularly ones from sweat glands.
Electroencephalogram or EEG: An EEG can assist a doctor to see unique patterns in the electrical activity of the person's brain that suggests they have seizures.
Electrical studies of the eyes: Electrical studies of the person's eyes include visual-evoked responses and electro-retinograms, which may detect a number of eye problems that are common in children with NCL's.
Brain scans: Brain imaging can help a doctor to look for changes in the appearance of the person's brain. A CT scan can show areas of the person's brain that are decaying due to an NCL. An MRI may also be used.
Measurement of enzyme activity: A doctor can measure the activity of palmitoyl-protein thioesterase, involved in CLN1, and the acid protease, involved in CLN2, in the person's white blood cells, or cultured skin fibroblasts may be used in order to confirm diagnoses.
DNA analysis: A DNA analysis can be used to confirm the diagnosis, or for the prenatal diagnosis of the CLN3 form of Batten disease. When the mutation is known, a DNA analysis might also be used to detect unaffected carriers of the condition for genetic counseling.
There is potential for misdiagnosis related to Batten disease. Because any particular autosomal recessive disorder is rare and many times has complex symptoms, as well as laboratory results, diagnosis that are both accurate and timely are difficult. Batten disease is many times misdiagnosed as, 'retinitis pigmentosa.' Wilson's disease is a form of autosomal recessive genetic disorder that causes both liver and neurological problems. Wilson's disease also causes psychiatric problems, to include depression, behavioral changes, psychosis and anxiety, and is many times misdiagnosed as schizophrenia. Differentiating among rare conditions often relies on evidence that is subtle and circumstantial; even the most experienced clinicians can find it to be difficult because many autosomal recessive disorders share similar features.
Treatment of Batten Disease
Medical science has not yet discovered a specific treatment that will either stop of reverse the symptoms of Batten disease at this time. Seizure activity may sometimes be either reduced or controlled through the administration of anticonvulsant medications. Other medical problems may be treated as they arise. Both occupational and physical therapies can assist people with Batten disease to retain levels of functioning as long as possible.