Infantile neuroaxonal dystrophy (INAD) is a rare neurodegenerative illness with a life expectancy of about 10 years.
INAD is characterized by regression of acquired motor abilities, delayed motor coordination, and ultimately loss of voluntary muscle control beginning at about 6 months of age.
INAD is a progressive condition, with symptoms worsening over time. In general, there may be a decline in vision, speech, and mental functions. Death typically occurs between the ages of 5-10 years.
What are the symptoms of infantile neuroaxonal dystrophy?
Infantile neuroaxonal dystrophy (INAD), also known as Seitelberger's disease, is a rare autosomal recessive neurological illness that damages axons, which are nerve fibers that convey information from the brain to other parts of the body.
INAD symptoms appear within the first 2 years of life, and some individuals are born with facial malformations. INAD affects the brain and other sections of the body, resulting in a gradual loss of eyesight, as well as physical and mental abilities.
Symptoms of INAD may include:
- Facial deformities at birth (prominent forehead, small nose and jaw, crossed eyes, and low-set ears)
- Inability to hold up the head
- Poor muscle tone
- Loss of ability to sit, stand, crawl, and walk
- Loss of coordination
- Problems chewing, coughing, and swallowing
- Deterioration in vision and speech
- Hearing loss
- Recurrent episodes of apnea that occur during infancy
- Pneumonia due to the aspiration (breathing in) of food, liquid, or gastric contents into the upper respiratory tract
In the final phases of the disease, the child will be completely unresponsive to their environment.
What causes infantile neuroaxonal dystrophy?
Although the underlying genetic and metabolic causes of the disease are unclear, infantile neuroaxonal dystrophy (INAD) is caused by an accumulation of harmful chemicals within the nerves that interact with the skin, muscles, and eyes.
Studies have shown that INAD is a hereditary disorder caused by a mutation in one or more genes, typically the PLA2G6 gene. This gene codes for an enzyme called A2 phospholipase, which is required for the breakdown of lipids (a form of fat). When the PLA2G6 gene is defective, the breakdown of lipids is disrupted, which can lead to an excess accumulation of membranes in nerve terminals and, eventually, iron buildup in the brain.
INAD is inherited as an autosomal-recessive trait. This condition is only possible when both parents are either affected or gene carriers for this disease. Research shows that INAD may occur in less than 1 in 200,000 children.
INAD is distinguished by the formation of spheroid bodies in the axons, which are fibers that stretch from nerve cells (neurons) and convey impulses to the muscles and other neurons. Abnormal amounts of iron build in a specific area of the brain called the basal ganglia in certain people with INAD. It is uncertain how these characteristics relate to the symptoms of INAD.
How is infantile neuroaxonal dystrophy diagnosed?
Magnetic resonance imaging (MRI) of the brain and an ophthalmologic exam are the primary tests used to diagnose infantile neuroaxonal dystrophy (INAD). Although electrophysiology (nerve conduction velocities) can aid in the diagnosis, a tissue biopsy of the skin, rectum, nerve, or conjunctive tissue is typically required to establish the presence of distinctive swellings (spheroid bodies) in the nerve axons.
Diagnostic options for INAD include:
- Examine a sample of the skin or conjunctiva under a microscope and establish the existence of spheroid bodies in the nerve axons contained inside it.
- Typically, the PLA2G6 gene will be tested on a blood sample first, which may confirm the diagnosis without the need for biopsies.
- Prenatal testing for INAD is now available due to recent developments in genetic research if the PLA2G6 gene is detected in the infant.
- Characteristic brain imaging and rapid electroencephalogram (EEG) rhythms may support the decision to undergo molecular analysis rather than a skin sample to confirm the diagnosis.
- Electromyographic (EMG) and MRI anomalies are the first and most indicative symptoms of INAD, which has a larger clinical and radiologic spectrum than previously documented.
What are the treatment options for infantile neuroaxonal dystrophy?
There is no specific treatment available due to a lack of understanding regarding the etiology of infantile neuroaxonal dystrophy (INAD). Symptomatic and supportive care may be recommended, but there is currently no treatment that can stop or delay the illness itself.
Palliative treatment options for INAD include:
- Management of infections with medications
- Pain relief and sedative drugs as needed
- Feeding assistance
- Physiotherapy and advice on how to position, seat, and exercise the child’s limbs
Supportive care may include the following:
- Teachers for the visually impaired can advise parents on how to assist the child make the most of the vision they have and how to engage them in ways that do not rely on vision.
- Specialist education or schooling will be necessary, and it is critical for the child to have this stimulating atmosphere and social contact.
- Although not scientifically established, many children may benefit from alternative therapies such as cranial osteopathy and massage.
- A rehabilitation program that includes physiotherapy and orthopedic care may be beneficial and should begin early in the disease's progression. The primary goal of these therapies is to keep contractures and permanent deformities from developing.
- Spasticity and seizures should be handled with appropriate muscle relaxants and anti-epileptics.
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How does infantile neuroaxonal dystrophy progress to death?
Infantile neuroaxonal dystrophy (INAD) is characterized by psychomotor regression, which gradually leads to death.
Secondary issues, such as aspiration pneumonia or other infections, are generally the cause of death. Due to bulbar dysfunction, patients may come for gastrostomy tube and tracheostomy installation, and some may require surgical correction of scoliosis to improve respiratory status.
What does the research say about infantile neuroaxonal dystrophy?
Research is ongoing regarding degenerative neurological illnesses, and with the identification of the PLA2G6 gene mutation, it is anticipated that there will be an improved understanding of what the gene does and future gene treatments.
Potential promise in research of infantile neuroaxonal dystrophy (INAD) include the following:
- Ongoing clinical trials and studies indicate that gene editing may hold hope for a cure by directly repairing the disease-causing mutation. Gene editing is a technique with a lot of promise for aiding patients with rare genetic diseases.
- Researchers are still looking for the faulty genes that cause INAD in the hopes of discovering medications that will cure the condition.
- One study is investigating whether professionally administered desipramine may be successful in reducing symptoms and decreasing the course of INAD in children.
- Researchers are striving to discover therapies for the fundamental cause of INAD, which is defective PLA2G6 enzyme action.
- There is promising research on gene therapy for INAD, which involves screening chemical compounds for their ability to either improve the function of the PLA2G6 enzyme when it is impaired by INAD mutations or to stimulate other enzymes to compensate for the impaired PLA2G6 function.
Additional research is supported through grants to major medical institutes around the country. Much of this research focuses on discovering better ways to prevent, treat, and eventually cure diseases such as INAD.
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Infantile Neuroaxonal Dystrophy: Diagnosis and Possible Treatments: https://www.frontiersin.org/articles/10.3389/fgene.2018.00597/full
Infantile Neuroaxonal Dystrophy (INAD): https://www.raregenomics.org/infantile-neuroaxonal-dystrophy-inad
Infantile Neuroaxonal Dystrophy: https://unitedbrainassociation.org/brain-resources/infantile-neuroaxonal-dystrophy/
Infantile neuroaxonal dystrophy: https://rarediseases.oscar.ncsu.edu/disease/infantile-neuroaxonal-dystrophy/about/
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