Neurofibromatosis Type 1

Type 1 Neurofibromatosis (NF1) (also known as von Recklinghausen’s disease) is the more common of the two major types of the condition. It occurs in approximately 1 in 3000 individuals. The NF1 gene exists on chromosome 17, creating a specific type of regulatory protein for nerves. A mutation in this gene results in dysregulation and uncontrolled cell growth.

KEY FEATURES FOR DIAGNOSIS

(more than 2 of the following must be present)

• More than 6 café-au-lait macules
• More than 2 neurofibromas or 1 plexiform neurofibroma
• Optic glioma
• More than 2 Lisch nodules (iris of eye)
• Armpit or groin freckling
• Bone involvement
• Parent or sibling with Type I NF

Almost all people with NF-1 will have multiple café-au-lait spots from early childhood. These are flat patches on the skin that are darker than the surrounding area and have a characteristic light coffee-colored look. These spots increase in size and number as the individual grows. Freckles in the underarms and groin will develop later in childhood.

Neurofibromas are the hallmark of NF-1. These are  noncancerous (benign) tumors that are usually located on or just underneath the skin. They can be located virtually anywhere in the body including the nerves along the spinal cord. In a very small percentage of individuals, these tumors can become cancerous. These are called malignant peripheral nerve sheath tumors. There is also an increased risk of developing other cancers such as leukemia and brain tumors.

Lisch nodules are benign growths that occur along the colored part of the eye (or, the iris). They are seen typically during childhood but do not interfere with vision. However, another type of tumor called an optic glioma may result in reduced or complete loss of vision. These are benign tumors that grow along the optic nerve, which is responsible for transmitting signals from the eye to the brain. In some instances, these tumors must be removed.

There are other problems that can arise in patients with NF-1. High blood pressure, scoliosis, short stature, and learning disabilities.

Diagnosing NF-1 is usually done on physical exam and history. The criteria above are used to accurately identify people with NF-1. In some instances, genetic testing may be performed to identify the gene mutation that exists on chromosome 17. The normal variant of the gene is responsible for creating a protein called neurofibromin. This substance is created by the supporting cells that line and nourish nerves. It functions to suppress tumor formation in these cells. When a mutation occurs in its gene, a non-functional protein is produced, allowing uncontrolled growth of tumors.

In general, the inheritance pattern of NF-1 is autosomal dominant, meaning each mutated copy of the affected gene is passed on to the next generation. This is true in 50 percent of individuals who have been newly diagnosed. However, the remaining 50 percent result from a new mutation with no known family members exhibiting the condition.

What to do if you have been diagnosed with NF-1

If you or a family member are diagnosed with Type 1 neurofibromatosis, the first step is referral to a Neurofibromatosis Clinic or a neurologist or geneticist with expertise in the field. After a thorough workup, there may be a requirement to see a neurosurgeon if there are critical brain masses identified or an orthopedic surgeon for spine issues. Frequently, a plastic surgeon with specialization in neurofibromatosis is required to address tumors that are causing symptoms such as pain or disfigurement. Dr. Panossian has treated patients with neurofibromatosis for over a decade and recognizes the unique requirements of this patient population. Our office can assist you with the proper referral.