Neurofibromatosis type 1

Alternate names

NF1; Type 1 neurofibromatosis; Recklinghausen's disease; Von Recklinghausen disease

Definition

Neurofibromatosis type 1 (NF1) is a genetic condition that affects the skin, the skeleton and the part of the nervous system outside the brain and spinal cord peripheral nervous system).

Epidemiology

Neurofibromatosis type 1 occurs in 1 in 3,000 to 4,000 people worldwide.

Cause

• Mutations in the NF1 gene cause neurofibromatosis type 1.
• The NF1 gene provides instructions for making a protein called neurofibromin.
• This protein is produced in many cells, including nerve cells and specialized cells surrounding nerves (oligodendrocytes and Schwann cells).
• Neurofibromin acts as a tumor suppressor, which means that it keeps cells from growing and dividing too rapidly or in an uncontrolled way.

Gene mutations

• Mutations in the NF1 gene lead to the production of a nonfunctional version of neurofibromin that cannot regulate cell growth and division.
• As a result, tumors such as neurofibromas can form along nerves throughout the body.
• It is unclear how mutations in the NF1 gene lead to the other features of neurofibromatosis type 1, such as café-au-lait spots and learning disabilities.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

• Neurofibromatosis type 1 is considered to have an autosomal dominant pattern of inheritance. People with this condition are born with one mutated copy of the NF1 gene in each cell. In about half of cases, the altered gene is inherited from an affected parent. The remaining cases result from new mutations in the NF1 gene and occur in people with no history of the disorder in their family.
• Unlike most other autosomal dominant conditions, in which one altered copy of a gene in each cell is sufficient to cause the disorder, two copies of the NF1 gene must be altered to trigger tumor formation in neurofibromatosis type 1. A mutation in the second copy of the NF1 gene occurs during a person's lifetime in specialized cells surrounding nerves. Almost everyone who is born with one NF1 mutation acquires a second mutation in many cells and develops the tumors characteristic of neurofibromatosis type 1.

Signs and symptoms

Signs and symptoms may include:

• Non-cancerous growths along the nerves under the skin (cutaneous neurofibromas)
• Large growths along nerves that may become cancerous (plexiform neuromas)
• Dark spots of skin (café au lait spots)
• Freckling, especially in the underarm and groin
• Pigment in the colored part of the eye (Lisch nodules)
• Learning disabilities
• Seizures
• Autism spectrum disorder
• High blood pressure
• Short stature
• Large head (macrocephaly)
• Curvature of the spine (scoliosis)

• In many cases, the first symptom of neurofibromatosis type 1 (NF1) is multiple small dark colored birth marks known as café-au-lait spots.
• As they grow older, people with NF1 develop neurofibromas, benign tumors that can affect nearly any nerve in the body.
• These tumors usually grow on or just underneath the skin, but neurofibromas can also grow in other places in the body and may even affect multiple nerves. Some of these tumors can cause skin irritation, nerve damage, or affect a person’s appearance.
• In addition, some of these tumors may become cancerous.
• The most common type of cancerous tumors in people with NF1 are malignant peripheral nerve sheath tumors.

Diagnosis

The diagnosis will most likely be made based on the unique symptoms and signs of NF.

Signs include:

• Colored, raised spots (Lisch nodules) on the colored part (iris) of the eye
• Bowing of the lower leg in early childhood that may lead to fractures
• Freckling in the armpits, groin, or underneath the breast in women
• Large tumors under the skin (plexiform neurofibromas), which can affect the appearance and put pressure on nearby nerves or organs
• Many soft tumors on the skin or deeper in the body
• Mild cognitive impairment, attention deficit hyperactivity disorder (ADHD), learning disorders

Tests may include:

• Eye exam by an ophthalmologist familiar with NF1
• Genetic tests to find a change (mutation) in the neurofibromin gene
• MRI of the brain or other affected sites
• Other tests for complications

Treatment

• Referral to specialists for treatment of complications involving the eye, central or peripheral nervous system, cardiovascular system, endocrine system, spine, or long bones
• Surgical removal of disfiguring or uncomfortable discrete cutaneous or subcutaneous neurofibromas.
• Surgical treatment of plexiform neurofibromas is often unsatisfactory.
• Complete surgical excision, when possible, of malignant peripheral nerve sheath tumors.
• Treatment of optic gliomas is generally unnecessary as they are usually asymptomatic and clinically stable.
• Dystrophic scoliosis often requires surgical management, whereas nondystrophic scoliosis can usually be treated conservatively.
• Methylphenidate treatment often benefits children with attention-deficit/hyperactivity disorder.[1].

NIH genetic and rare disease info

• NIH info on Neurofibromatosis type 1

Neurofibromatosis type 1 is a rare disease.

Neurofibromatosis type 1 Resources
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