Definition & Facts
Neurofibromatosis is a genetic disorder that causes a variety of symptoms including neurofibromas. Neurofibromatosis type I is the most common and least severe type of neurofibromatosis.
Neurofibromatosis type I is inherited half of the time through a pattern of autosomal dominant inheritance. The other half of the time, it results from de novo genetic mutations, occurring in those without a family history of the disorder.
Symptoms of neurofibromatosis type I typically appear when one is very young or by the age of 10, and include the presence of neurofibromas. Neurofibromas can be dermal, spinal, or plexiform.
Symptoms & Complaints
Dermal neurofibromas tend to increase in quantity and size over a person's life. Pregnant women sometimes experience an increase in the amount of neurofibromas they have. Dermal neurofibromas can cause a person psychological distress due to the effect they have on their appearance.
Plexiform neurofibromas are somewhat similar to dermal ones, except these tumors originate from deep tissues within the skin. The growth of these tumors is not limited to a certain size; they can grow large, and they often cannot be removed. In rare cases, plexiform neurofibromas can become cancerous, forming malignant peripheral nerve sheath tumors.
In addition to the presence of neurofibromas, neurofibromatosis type I, the condition most associated with neurofibromas, causes a host of other symptoms. These include light brown spots on the skin at a very young age. Children from the ages of three to five may see freckles develop on the folds of the skin.
Other individuals with neurofibromatosis type I may have tiny bumps on the iris (also called Lisch nodules), but these do not typically affect vision. Optic nerve gliomas may also occur which can affect vision. Scoliosis and other bone deformities are additional symptoms of neurofibromatosis type I.
Neurofibromatosis type I occurs due to genetic mutations which are either inherited or manifest in those without a family history of the disorder. Neurofibromatosis type I is caused by a defect in the NF1 gene on chromosome 17. NF1 gene produces neurofibromin, which is a tumor suppressor that controls and inhibits the growth of certain cells. The mutation involved in neurofibromatosis type I renders this protein incomplete and unable to effectively inhibit growth.
Diagnosis & Tests
97 percent of those with neurofibromatosis type I are diagnosed by the age of eight. The diagnosis of neurofibromatosis type I usually involves a physical examination of the person who may or may not be suffering from the condition. Doctors who suspect neurofibromatosis type I will try to determine if the patient has a family history or medical history of this genetic disorder.
The doctor will examine the patient for the presence of axillary and inguinal freckles, optic nerve gliomas, bone deformities, Lisch nodules and other symptoms of neurofibromatosis type I. The doctor will order an eye examination to see if there are growths in the iris.
X-rays and other imaging studies may also be ordered to detect abnormalities and tumors. Some parents can have their child genetically tested before he or she is born via amniocentesis or chorionic villus sampling.
Treatment & Therapy
Many patients and parents opt for surgery to reduce the appearance of neurofibromas for cosmetic reasons. Neurofibromatosis that leads to significant pain may require surgery. It may also be necessary to remove a growth, particularly a plexiform neurofibroma that may become malignant or one that may damage otherwise healthy tissue. Although rare, certain neurofibromas can become cancerous and if they do, they may require treatments such as radiotherapy and chemotherapy.
There is no known cure for neurofibromatosis type I and treatment involves close monitoring. Blood pressure and signs of developmental delays will be closely monitored. The child's learning abilities will be monitored. Special education and speech therapy as well as psychotherapy and psychiatric medication may be utilized to treat behavioral and learning problems associated with neurofibromatosis type I.
Prevention & Prophylaxis