ABOUT NF
What are the neurofibromatoses?
The neurofibromatoses are a group of three genetically distinct but related disorders of the nervous system that cause tumors to grow around the nerves. Tumors begin in the cells that make up the myelin sheath, a thin membrane that envelops and protects nerve fibers, and often spread into adjacent areas. The type of tumor that develops depends on its location in the body and the kind of cells involved. The most common tumors are neurofibromas, which develop in the tissue surrounding peripheral nerves. Most tumors are non-cancerous, although occasionally they become cancerous over time.
Why these tumors occur still isn't completely known, but it appears to be mainly related to mutations in genes that play key roles in suppressing tumor growth in the nervous system. These mutations keep the genes - identified as NF1 and NF2 - from making specific proteins that control cell production. Without these proteins, cells multiply out of control and form tumors.
An estimated 100,000 Americans have a neurofibromatos is (the singular form of neurofibromatos es ) disorder, which occurs in both sexes and in all races and ethnic groups. Scientists have classified the disorders as neurofibromatosis type 1 ( NF1 ), neurofibromatosis type 2 ( NF2 ), and a type that was once considered to be a variation of NF2 but is now called schwannomatosis .
What is NF1?
NF1 is the most common neurofibromatosis, occurring in 1 in 3,000 to 4,000 individuals in the United States . Although many affected people inherit the disorder, between 30 to 50 percent of new cases occur because of a spontaneous genetic mutation from unknown causes. Once this mutation has taken place, the mutant gene can be passed on to succeeding generations.
What are the signs and symptoms of NF1?
To diagnose NF1, a doctor looks for two or more of the following:
- six or more light brown spots on the skin (often called "cafe-au-lait" spots), measuring more than 5 millimeters in diameter in children, or more than 15 millimeters across in adolescents and adults;
- two or more neurofibromas, or one plexiform neurofibroma (a neurofibroma that involves many nerves);
- freckling in the area of the armpit or the groin;
- two or more growths on the iris of the eye (known as Lisch nodules or iris hamartomas);
- a tumor on the optic nerve (optic glioma);
- abnormal development of the spine (scoliosis), the temple (sphenoid) bone of the skull, or the tibia (one of the long bones of the shin);
- a first degree relative (parent, sibling, or child) with NF1.
What other symptoms or conditions are associated with NF1?
Many children with NF1 have larger than normal head circumference and are shorter than average. Hydrocephalus, the abnormal buildup of fluid in the brain, is a possible complication of the disorder. Headache and epilepsy are also more likely in individuals with NF1 than in the normal population. Cardiovascular complications are associated with NF1, including congenital heart defects, high blood pressure (hypertension), and constricted, blocked, or damaged blood vessels (vasculopathy). Children with NF1 may have poor linguistic and visual-spatial skills, and perform less well on academic achievement tests, including those that measure reading, spelling, and math skills. Learning disabilities, such as attention deficit hyperactivity disorder (ADHD), are common in children with NF1.
When do symptoms appear?
Symptoms, particularly the most common skin abnormalities -- café-au-lait spots, neurofibromas, Lisch nodules, and freckling in the armpit and groin -- are often evident at birth or shortly afterwards, and almost always by the time a child is 10 years old. Because many features of these disorders are age dependent, a definitive diagnosis may take several years.
