A rare genetic disorder, giant axonal neuropathy, affects the central nervous system (the brain and spinal cord) and the peripheral nervous system (the nerves in the rest of the body). The ]]>National Institute of Neurological Disorders and Stroke (NINDS)]]> notes that symptoms start before age five. Patients with giant axonal neuropathy have abnormally large axons, which are part of the neuron, that do not function properly. As the damage to the nerves become more severe, patients have more problems with movement, sensation and mental functions.
The ]]>Genetics Home Reference, a service of the US National Library of Medicine]]>, explains that mutations to the GAN gene can result in giant axonal neuropathy. The GAN gene contains instructions for the production of the protein gigaxonin. Multiple mutations can occur to the GAN gene. For example, some giant axonal neuropathy patients may have a mutation that affects how the gigaxonin protein binds to other proteins. Another mutation can affect the shape of the protein or may prevent the production of the gene. These mutations to the GAN gene cause to giant axons to not transmit signals as they normally would, leading to their deterioration.
Giant axonal neuropathy has an autosomal recessive pattern of inheritance. This means that to have giant axonal neuropathy, the patient must have two copies of the gene—one from each of her parents. A parent who only has one copy of the gene usually does not have any symptoms. The Genetic Home Reference points out that the number of people who have giant axonal neuropathy is not known.
The symptoms of giant axonal neuropathy start as clumsiness and muscle weakness. The NINDS notes that as the deterioration to the giant axons continue, patients develop a waddling gait, which results in difficulty walking. Giant axonal neuropathy patients have dull and kinky hair, which differs from their parents.