About Neurofibromatosis Type 1
Neurofibromatosis types 1 and 2 (NF1 and NF2) are genetic disorders. NF1 and NF2 are different conditions. They are frequently discussed together and often confused for one another. Both disorders have widely variable presentations and degrees of severity. Each one will be described separately.
Frequently Asked Questions
What is neurofibromatosis type 1 (von Recklinghausen Disease)?
NF1 is a common genetic disorder that affects approximately 1 in 3,000 people. About half of those affected with NF1 will have other affected family members. NF1 follows a clear autosomal dominant inheritance pattern, meaning that if a parent is affected there is a 50 percent chance for each child being affected with NF1. Often with autosomal dominant conditions, you will see the disease in every generation of a family. However, the remaining half of those affected with NF1 will be the only members in their family and will have no other affected family members. This is a result of spontaneous gene mutation that occurred at the moment of conception for reasons that are not entirely clear.
What is the NF1 gene and where is it located?
The gene for NF1 has been identified and is located on the long arm of chromosome 17; specifically 17q11.2.
What are the symptoms of NF1?
The symptoms vary widely from person to person. Most people with NF1 will have some but not necessarily all of the following:
How is NF1 diagnosed?
- Café-au-lait spots - Café-au-lait spots are flat, brown spots on the skin that usually appear during first year of life but are often present at birth. They may increase in number and size with age but often fade later in life. Café-au-lait spots are common; 25 percent of the general population has between 1 and 3 of these spots. In people affected with NF1, more than 95 percent of patients have them. For the purpose of diagnosing NF1, there needs to be a minimum of 6 café-au-lait spots that are greater than 5mm in diameter in children/ greater than 15mm in diameter in adolescents and adults.
- Freckling - People with NF1 often develop clusters of freckles in the armpits and groin. Freckling usually is not present at birth and often develops during childhood. It most commonly occurs in the armpits and groin areas but can occur in other parts of the body, particularly in skin folds.
- Neurofibromas - These are benign tumors that are present in the covering of the nerve cells. There are three main types of neurofibromas: cutaneous, subcutaneous and plexiform.
Cutaneous neurofibromas are soft fleshy tumors arising from the peripheral nerve sheath, often appearing in late childhood or young adulthood. They can become cosmetically significant and can cause itching or discomfort but do not become cancerous.
Subcutaneous neurofibromas are firm, tender nodules along the course of peripheral nerves beneath the skin that may appear during adolescence or young adulthood. Plexiform neurofibromas can involve long portions of one nerve or bundles of nerves. They can be deep inside the body and able to be seen only with medical scans (such as MRI, CT scans or ultrasounds), or they can be superficial and involve the skin, extremities, head or neck. When they occur they are typically present at birth though may not be apparent at first. They most commonly appear as a soft mass under the skin. Sometimes the skin overlying it may be darker than the surrounding skin and/or thickened. They tend to grow with age and can sometimes become disfiguring.
- Lisch nodules - These are raised, usually pigmented bumps (hamartomas) on the iris (colored part) of the eye that are best seen with a slit lamp examination by an ophthalmologist. They rarely cause any problems. Lisch nodules are most commonly seen in late childhood.
- Optic pathway gliomas (brain tumors) - Optic pathway gliomas are tumors that arise on the nerve pathways of the eyes and occur in up to 15 percent of children affected with NF1. They can appear anywhere along the optic pathways. They are typically slow-growing and benign. Only about 1/3 of optic gliomas are symptomatic. In patients who do have symptoms they may develop vision loss or bulging of an eye. They may also be accompanied by premature onset of puberty if the tumor originates near the middle of the brain. The tumors that are destined to become symptomatic or progress typically do so during the first decade of life, so yearly ophthalmologic evaluation is particularly important in children with NF1.
- Bone abnormalities - Bone abnormalities sometimes seen in NF1 include pseudarthrosis (or "false joint"), sphenoid wing dysplasia (malformation of the eye socket), vertebral dysplasias (abnormal shape of the bones of the spine), short stature and scoliosis (curvature of the spine). Pseudarthrosis or "false joint" occurs when a bone fractures and does not heal properly, or when bowing becomes so extreme that is causes a severe angle of the bone. This happens most often in the weight bearing bones, especially the tibia, the main bone of the lower leg. Pseudarthrosis occurs in up to 5 percent of patients affected with NF1. Half of all cases generally occur before 2 years of age. The treatment for pseudarthrosis can be complicated and requires the care of an orthopedist.
Sphenoid wing dysplasia or malformation of the eye socket is a malformation of one of the bones behind the eye. This can sometimes result in bulging or displacement of the eye. When it occurs, it is typically present at birth.
Vertebral dysplasia or abnormal shape of the bones of the spine may occur if neurofibromas begin to erode the bones of the spine or it may occur as a result of abnormal development and growth of the bones in the spinal column. It is often associated with scoliosis, or curvature of the spine.
People affected with NF1 can be tall or short. In general, there are broad variations with height for all people. However, about 80 percent of people with NF1 are shorter than their relatives or their peers.
Scoliosis, or curvature of the spine, can occur in up to half of people affected with NF1. If it occurs, it most commonly begins just before or during puberty. If the curvature is mild no treatment is necessary, however, in some patients bracing or surgery becomes necessary.
- Brain abnormalities -
Macrocephaly, or large head size, occurs in up to half of children with NF1. It is usually due to increased brain size, the cause of which is unclear.
Learning problems are commonly seen in the general population but are more common among those affected with NF1. About 1/2 to 2/3 of the NF1 population has learning disabilities. Intelligence is typically normal, though IQ tends to be 5-10 points lower in comparison to the general population or unaffected siblings. Attention-Deficit Hyperactivity Disorder (ADHD) is also probably more common in those affected with NF1 as well.
The diagnosis of NF1 is most often made on the basis of presence of specific physical findings. Some of the physical features of NF1 are not obvious until a child is older than 5 years of age. Practically all (97 percent) of those affected with NF1 will have enough features of the disorder to make the diagnosis by 8 years of age. The National Institutes of Health has set certain criteria to make the diagnosis of NF1. According to these criteria, NF1 is present in a person who has 2 or more of the following signs:
Is genetic testing available for NF1?
- Six or more café-au-lait spots (5mm in greatest diameter in prepubertal individuals of 15mm in greatest diameter after puberty)
- Two or more neurofibromas of any type or one plexiform neurofibroma
- Freckling in the axillary or inguinal regions
- A tumor of the optic pathway
- Two or more Lisch nodules
- A distinctive bone lesion, such as sphenoid wing dysplasia, or thinning of the cortex of the long bones (with or without pseudarthrosis)
- An affected first degree relative by the above criteria
Currently, the diagnosis of NF1 is made based on physical characteristics. Genetic testing, which is available through a blood test, generally will not assist in making the diagnosis. Current genetic testing has limitations, as laboratory technology is not able to determine with 100 percent accuracy the presence of a gene mutation. Testing is currently about 95 percent accurate. If no gene mutation is identified, NF1 is still a possible diagnosis. If a gene mutation is identified, the diagnosis is confirmed.
Knowing the genetic status of the NF1 gene is unlikely to change how children and adults are cared for or monitored.
How is NF-1 managed?
NF1 affects many systems throughout the body. Therefore, a multidisciplinary team approach to management is often followed. Patients with NF1 should undergo twice yearly physical examinations at least until age 5 and then yearly thereafter. Blood pressure should be checked at least twice yearly. Special attention should be paid to early detection of scoliosis, evidence of bone changes, monitoring skin manifestations, and signs of precocious or delayed puberty. Head circumference should be checked regularly, particularly in the first three years of life. Behavior and development should be followed carefully for signs of learning disability and ADHD.
Patients with NF1 should also undergo yearly neurologic and ophthalmologic evaluation. As part of a comprehensive care team, patients will be appropriately referred to specialists who are familiar with and have experience in caring for individuals with NF1. The team approach to caring for people with NF1 generally consists of specialists in the following areas: cardiology, dermatology, developmental pediatrics, endocrinology, ENT (ear-nose-throat), genetics, neurology, neuro-oncology, neuro-radiology, neurosurgery, ophthalmology, orthopedics, plastic surgery, radiation oncology, radiology, and surgery.
Where can I learn more about NF1?
It is important to remember that often information found on the Internet can be incorrect, biased and sometimes very scary. NF1 has a variety of features and symptoms. Often, Internet sites focus on sharing the worst case scenarios. For non-biased, medically sound information on NF1, helpful resources include:
Children's Tumor Foundation, which is dedicated to NF research and information/support
Neurofibromatosis Inc., a national support and advocacy group