Infantile Neuroaxonal Dystrophy (Seitelberger Disease)
What is Infantile Neuroaxonal Dystrophy ?
Infantile neuroaxonal dystrophy (INAD) is a rare neurological disorder that causes gradual loss of vision and impaired movement and speech. This progressive condition occurs when the nerve axons, the parts of the nerves responsible for transmitting signals, don’t work properly.
INAD may sometimes be referred to as Seitelberger’s disease. This is after the doctor who first described its characteristics during the 1950s.
INAD is rare. Although the exact incidence is unknown, it is thought to affect around 1 in every 200,000 children.
What causes infantile neuroaxonal dystrophy?
INAD occurs when abnormal deposits collect in the nerves. These collections are known as spheroid bodies and they prevent the nerves from working normally. Most commonly, spheroid bodies are found in the nerve endings in the conjunctiva, skin and muscle tissue. It is not fully understood why these deposits collect in the nerve endings, but experts believe that this may be a by-product of the systems that usually dispose of unwanted substances not functioning properly.
INAD is an inherited disorder and it follows an autosomal recessive inheritance pattern. When a disorder is recessive, this means that a copy of the defective gene must be passed on by both parents in order for a child to develop the disorder. With each pregnancy, there is a:
- 25% risk of the child being affected
- 25% risk of the child being unaffected
- 50% risk of the child being a carrier (this means they have one gene, but they won’t develop symptoms)
In the past, INAD was only diagnosed following detailed analysis of a sample of tissue from the conjunctiva or the skin under a microscope. However, nowadays it is possible to perform genetic testing, which involves testing the PLA2G6 gene. This may make it possible to confirm a diagnosis without the need to remove and analyse tissue biopsies.
It is possible to perform antenatal testing if the PLA2G6 gene has been identified.
What are the symptoms?
Symptoms tend to develop after the age of 6 months and before this, development appears normal. Between the ages of 6 months and 2 years, development starts to slow down and as time progresses. Children lose previously acquired skills and start to develop symptoms such as:
- gradual loss of vision, squinting, rapid, darting eye movements and eventual blindness
- stiffness in the limbs
- loss of awareness of the surrounding environment
- difficulties with feeding and swallowing
- becoming floppy and losing muscle tone (known as hypotonia)
- increased risk of infections
- increasing weakness
As symptoms progress children become increasingly dependent on their parents and the care team. Most children will die between the ages of 5 and 10 years old.
How is INAD treated?
There is no cure for INAD at the moment and treatments are focused on improving quality of life and alleviating symptoms.
Medication can help to treat infections and ease any discomfort and physiotherapy can help with feeding and strengthening the muscles to improve movement. Special needs teachers in schools can provide additional support for children and help can also be provided to help children cope with loss of sight and adapt their way of living. There is no scientific evidence to support the efficacy of complementary therapies. However, some parents have found that therapies such as massage can be helpful.
Research into treatment options is ongoing.