GAN-related neurodegeneration, also known as Giant Axonal Neuropathy (GAN), is a rare inherited neurological condition that affects the peripheral and central nervous systems. It is caused by disease – causing gene changes in the GAN gene, which provides instructions for making a protein called gigaxonin. This protein plays a crucial role in maintaining the normal structure and function of nerve cells.
When gigaxonin is not working properly due to a disease – causing gene change in the GAN gene, the nerve fibres, particularly the axons that carry electrical signals, begin to swell and malfunction. Over time, this leads to the progressive loss of nerve function, resulting in muscle weakness, coordination difficulties, and other neurological symptoms.
What Are the Symptoms?
Children with GAN typically appear healthy at birth and usually develop normally for the first few years of life. Early signs often appear in early childhood and may include:
- Unsteady walking or frequent falls
- Muscle weakness (particularly in the legs)
- Reduced reflexes
- Curly or frizzy hair (a distinctive but not universal feature)
As the condition progresses, muscle weakness and loss of coordination worsen, leading to difficulties with walking, standing, and eventually mobility. Many affected individuals require a wheelchair by adolescence.
Over time, other parts of the nervous system can also be affected. This may result in vision loss, hearing loss, speech difficulties, seizures, and respiratory problems. Although the rate of progression can vary, GAN-related neurodegeneration is typically a progressive and life-limiting condition.
The Genetic Cause
GAN is inherited in an autosomal recessive pattern. This means that a person must inherit two copies of the non-working GAN gene, one from each parent, to develop the condition. Parents who each carry one copy of the mutation are known as carriers. Carriers do not usually show symptoms but two carriers together have a 25% chance of having an affected child with each pregnancy.
Genetic testing is essential for confirming a diagnosis. Testing can identify changes in the GAN gene and can also determine whether parents or siblings are carriers. Early diagnosis can help families access appropriate medical care, support services, and genetic counselling.
Diagnosis and Management
Because GAN is rare, diagnosis can sometimes take years. Neurologists and other clinicians may first suspect the condition based on neurological examination, nerve conduction studies, or MRI findings that show abnormalities in the brain’s white matter. However, molecular genetic testing is the definitive way to confirm the diagnosis.
There is currently no cure for GAN-related neurodegeneration. Management focuses on supportive care to improve quality of life and manage symptoms. This may include:
- Physiotherapy and occupational therapy to maintain mobility and strength
- Speech and respiratory therapy
- Regular neurological and ophthalmological follow-up
- Assistive devices for mobility and communication
Promisingly, research into gene therapy is underway in some countries, aiming to replace the faulty GAN gene with a functional one. While still experimental, early studies offer hope for slowing or halting disease progression in the future.
Genetic Counselling and Family Planning
For families affected by GAN, genetic counselling can provide vital information and support. Counsellors can discuss carrier testing for family members, reproductive options such as preimplantation genetic testing (PGT-M) through IVF, and prenatal testing for future pregnancies.
Understanding carrier status empowers families to make informed reproductive choices and can help identify other at-risk relatives.
Final Thoughts
GAN-related neurodegeneration is a devastating but rare condition, highlighting the importance of early genetic diagnosis and family support. Advances in gene therapy and precision medicine continue to bring hope to affected families worldwide.
At Rosalind Genetics, we’re dedicated to improving access to genetic testing and counselling for all families, helping them understand complex genetic conditions and make informed choices about their health and future.
