Batten diseases is rare but fatal genetic disorder. It was first reported in 1983 by Dr. Frederick Batten. Batten disease is a rare autosomal recessive inherited disorder. It is mainly characterized by problems with the nervous system. It belongs to a group of disorders called Neuronal Ceroid Lipofuscinoses (NCL). It begins in childhood and is found in adults too. Batten disease is one of the most common forms of NCL. It is one of the 50 forms of lysosomal storage disease (LSD). Due to genetic mutations, the cells' (of brain and central nervous system) lysosome lose their ability to remove the waste or excess material of the cells. As a result, the waste material accumulates in the cell and causes problems.
Types of Batten Disease
There are various forms of Batten diseases. These are classified by the age of onset and the type of genetic mutations involved like Infantile Neuronal Ceroid Lipofuscinoses, late infantile and juvenile (or adult) Neuronal Ceroid Lipofuscinoses. Among these, Juvenile Neuronal Ceroid Lipofuscinoses is the most common form of Batten disease. Nearly 10-20 genes have been implicated in causing Batten diseases.
Congenital Batten Disease: This type of Batten disease is very rare and babies die soon after birth.
- Infantile Batten Disease: It begins within 6 months to 2 years of age and has a very rapid progress. These children die by 5 years of age or else they remain in vegetative state. There is genetic mutation with CLN1 gene which encodes for protein PPT1.
- Late Infantile Batten Disease: Late infantile Batten Disease is seen from the age of 2 to 4 years and progresses rapidly. These children have life span till 8 to 12 years of age. There is genetic mutation in gene CLN2 which encodes for the protein TPP1 which functions as a lysosomal enzyme.
- Adult Batten Disease: It is also called Kufs disease and has a late onset of 40 years. Adults show mild symptoms with slow progress of disease. They too have short life span.
There are variants of late infantile Neuronal Ceroid Lipofuscinoses.
Symptoms of Batten Disease
The child with Batten disease starts with a normal development but by the age of 5-10 years shows the symptoms of epileptic seizures and blindness. Other symptoms of Batten Disease involve personality and behavioral changes such as:
- Jerks of limbs
- Slow learning with slow growth of head
- Less blood circulation in lower extremities
- Insomnia (difficulty in sleeping)
- Loss of mobility
- Problem with speech
These are extremely strange symptoms and difficult to be managed by the caretakers. Over the time the children with Batten disease lose their mobility, sight, speech and get frequent seizures due to which they become bedridden. Finally, death is inevitable in such patients.
Epidemiology of Batten Disease
Batten disease is a rare disease. The frequency of occurrence of the disease is 2-4 in 100,000 live births. It is commonly seen in countries such as Sweden, Finland, Europe and Canada. Both males and females suffer from Batten disease. Females with juvenile Batten disease have short life span than males. When it occurs in a family, generally it affects more than one individual in that family.
Prognosis of Batten Disease
There is no cure for Batten disease and death is evident. Thus, all forms of Batten disease have poor prognosis and show a short life span.
Causes of Batten Disease
Batten disease is a genetic disorder caused due to defects in genes involved in lysosomal storage functions. The exact reason of what causes the genetic defect is not known.
Batten disease is an inherited autosomal recessive disorder. It means that both chromosomes carry mutations in the disease gene, and both parents are unaffected carriers. The child gets the disease when one copy of the defective gene is passed from each parent. The child possesses two copies of the defective gene and shows clinical manifestations of Batten Disease. The individual who carries one copy of the defective gene is known as the carrier and passes this gene to the offspring's but does not get affected themselves.
Pathophysiology of Batten Disease
Batten disease primarily affects the nervous system. The genetic defect affects lysosome functions. There is excessive accumulation of substances called as lipopigments (lipofuscin) in the cells of the brain. These lipopigments are made of fats and proteins and accumulate in different body tissues such as retina, skin, muscles, and central nervous system. This accumulation affects functions of neurons and leads to their death. The changes are seen in the form of progressive symptoms.
These lipopigments show greenish-yellow color under UV light microscope. They form deposits inside the cells which are seen as half-moon shapes, fingerprint or sand grain shapes.
Complications of Batten Disease
Batten disease is a neurodegenerative disease which begins in the childhood. The patient exhibits a lot of symptoms which are difficult to deal with even by the caretakers. The presence of seizures and slipping into coma are the main complications. The patient survives only till twenty years of age.
Diagnosis of Batten Disease
The first sign of Batten disease is problem with the vision which has to be diagnosed by the doctor as the beginning of this disorder. The doctor performs physical examination and notes down the medical history. The patient will be advised to do a number of tests which are as follows:
- Blood Tests to Diagnose Batten Disease: Microscopic analysis to detect the presence of lymphocytes with vacuoles (holes or cavities).
- Urine Tests for Batten Disease: This indicates the presence of elevated levels of a chemical called dolichol.
- Diagnosing Batten Disease with Skin Biopsy: Electron microscope observation of skin tissue reveals the abnormal storage of pigments inside the cells.
- Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) Scans to Diagnose Batten Disease: These diagnostic imaging tests allow visualizing the appearance of brain. These help to reveal if the brain areas are decaying and shrinking in size.
- Electroencephalogram (EEG): In this technique, the probes are attached to the patient's scalp to analyze electrical pattern activity in the brain with regards to the seizures. Electroretinograms to detect the eye conditions which are characteristic of Batten disease.
- Determination of Enzyme Activity to Diagnose Batten Disease: Measurement of activity of enzymes palmitoyl-protein thioesterase, CathepsinD and Acid protease. These enzymes are specific for specific type of Neuronal Ceroid Lipofuscinoses and help in differential diagnosis of Batten disease.
- Genetic or DNA Analysis: This helps to detect the exact defective gene in the affected person. Similarly, it also helps to detect the defective gene in carrier and helps to identify the family mutation.
Treatment of Batten Disease
Till date there is no treatment for Batten disease. Drugs are available to control seizures and mental problems. Physical and occupational therapy may be helpful. However, there are no drugs which can cure Batten's disease. Only palliative care is given to alleviate the symptoms.
Batten disease is a fatal genetic disorder which affects lysosome of the brain cells. It exhibits a number of symptoms which are difficult to manage. It is a complicated disorder which ultimately leads to death of an individual. There is still no known cure and the condition is managed with anti-epileptic drugs. Since it is a single gene disease hence emphasis is given to the molecular based treatments such as the gene therapy, stem cell therapy and immunosuppression, etc. These are still in research phase and clinical trials will be done before used in clinics.