Created: Monday, November 12, 2007
Amyloid is a immune deposit that can be formed by abnormal autoimmune proteins. In some cases, these amyloid deposits can form on nerves throughout the body, leading to injury and nerve
dysfunction. Amyloid neuropathy can be difficult to treat because it is a systemic disease, though medications for the symptoms can be prescribed.
Amyloidosis describes a series of disorders in which an abnormal protein causes problems throughout the body. One form of amyloidosis that can cause neuropathy in the peripheral nervous system is due to a problem with the protein transthyretin. This protein, according to Neoucom.edu, is made by the liver. Mutated forms of transthyretin are the most common cause of a class of diseases known as familial amyloid neuropathies.
Transthyretin mutations that cause familial amyloid neuropathies affect approximately one in every 100,000 Americans, states the Genetics Home Reference website. This condition is much more common in Portugal where it is thought to affect one in every 538 people. Most cases of this type of amyloidosis are due to mutations in a gene called TTR. Transthyretin amyloidosis is an autosomal dominant disease, which means that patients only need to have one mutated copy of the gene to get the disease. In most cases, the condition is inherited from the patient's parents, although patients can develop new mutations during their lifetime.
Patients with amyloid neuropathies develop deposits of abnormal protein on their nerves, which leads to nerve damage, according to the Johns Hopkins Medicine website. If sensory nerves are affected, patients may develop numbness or unusual sensations in parts of their body. They may also develop troubles with balance. Damage to other kinds of nerves, called autonomic nerves, can lead to persistent nausea, sweating, constipation/diarrhea, incontinence and sexual dysfunction.
The medical history of both the patient and the family is important for a diagnosis of amyloid neuropathy because of the genetic component to this disease. Along with a physical exam, additional tests may be needed to diagnose the patient's condition. Electromyography helps measure the ability of the nerves to conduct impulses and can determine which nerves are affected. A biopsy of the affected nerve can then be done to look for amyloid deposits, using a microscope. Patients may also want to have a genetic test performed to see if they have one of the known mutations that causes amyloid neuropathy.
Many patients with amyloid neuropathy will have the progression of their disease slowed as a result of a liver transplant, Neoucom.edu explains. Pain from the neuropathy can be treated with anticonvulsants such as gabapentin, topiramate and pregabalin. Antidepressant medications, such as amitriptyline, can also be effective for pain relief. Opioid medications can be used to relieve pain as well, although they tend to be less effective for neuropathic pain than other types of pain.