Neurofibromatosis is an uncommon genetic disorder where multiple lesions from primitive cells grow on nerves or within the nervous system such as the spinal cord and brain. The tumors can also affect other parts of the body. The growths are often flat although they can be raised. These growths are usually benign but can turn cancerous (malignant). Changes in pigmentation or skin coloring also mark neurofibromatosis. This condition typically manifests in infancy or early adulthood. Complications may include loss of vision, loss of hearing, severe pain, cardiovascular issues, and learning impairment.
The three types of the disorder include:
Neurofibromatosis type I (NF1)
- Von Recklinghausen disease
- Peripheral neurofibromatosis
- Recklinghausen disease, nerve
- Von Recklinghausen’s neurofibromatosis
Neurofibromatosis type II (NF2)
- Central neurofibromatosis
- Bilateral acoustic neurofibromatosis
- Vestibular schwannoma neurofibromatosis
Causes & Risk Factors
Neurofibromatosis is either inherited or caused by a gene mutation. Chromosome 17 causes type 1, while chromosome 22 causes type 2 and is passed on from parent to child. Neurofibromin is a protein produced by the NF1 gene and assists in regulating the growth of cells. Mutations of this gene can lead to uncontrolled growth, hence the tumors. The NF2 gene produces the protein merlin, which suppresses tumors. When the gene mutates, merlin is lost, so that cell growth is not controlled.
Schwannomatosis is caused by the mutations of SMARCB1 and LZTR1 genes responsible for suppressing tumors. A family history of the condition constitutes the primary risk factor.
Signs & Symptoms
The signs and symptoms depend on the type of neurofibromatosis.
- Congenital (present at birth) or manifests during early childhood
- Deformed and enlarged bones
- Benign tumors may develop under the skin
- Scoliosis (spine curvature) due to abnormal bone growth
- Malignant tumors affecting the spinal cord, brain, or cranial nerves
- Affected children may have larger than average size heads or have a below-average height (short stature)
- It affects family members differently where some have mild symptoms while others have severe symptoms
- Several light brown freckles in the underarms, in the bend of the knee and elbow, and groin. The spots increase in number in the first ten years of life
- Irregularly shaped and thick eyelids which can lead to amblyopia or glaucoma. Lisch nodules (pigmented spots), which do not affect vision, may develop on the iris and increase in number with time. Growths may also occur on the choroid (in the inner eye) but will not affect vision. A glioma (benign tumor) may grow on the optic nerve and cause problems with vision. The sphenoid (a bone around the eye) may fail to develop well due to the growths causing eye pulsation (throbbing).
- Develops in childhood, teens, or early adulthood and is less common than NF1
- There may be other problems such as early cataract, nervous system tumors, and spots on the iris
- Tumors affect the right and left auditory nerves. They grow in the eye so that the affected person develops hearing problems. The tumors also grow on the nerves, which send information on balance and sound, to the brain and inner ear. The affected person has poor balance, headaches, ringing in the ears, and gradually loses sense of hearing
- It develops in adults aged 30 and above and is rare
- It shares many characteristics of NF1 and NF2
- Tumors develop on the peripheral, spinal, and cranial nerves
- Symptoms include loss of muscle, body weakness or numbness, chronic and sometimes disabling pain anywhere in the body
Diagnosis is primarily made based on symptoms of the three types of neurofibromatosis. The following can also assist with diagnosis:
- Patient and family medical history
- Genetic testing to diagnose NF1 and NF2
- Use of a special lamp to examine the skin to help diagnose NF1
- An eye examination where the doctor can detect cataracts and Lisch nodules
- An audiometry test that records eye movements through electrodes to measure hearing
- Electronystagmography test for hearing and balance assessment in those affected by NF2
- Imaging tests such as a CT scan, MRI, or X-ray to provide pictures of tumors in the spinal cord and brain and show abnormalities involving the bones
There is no known cure. Treatment aims to promote development and healthy growth in the affected children and manage the resultant complications.
Pain medications are prescribed to control pain. For those with hearing loss due to NF1, cochlear and auditory brainstem implants can help.
Surgery is recommended when the tumors grow too large so that they press on a nerve. The growths may cause ptosis on the eyelid, prompting for surgery. Gliomas may only require observation, but lesions in the optic nerve may be removed. If the tumors involve the brain, chemotherapy and radiation are performed.
Prognosis & Long-Term Outlook
There may be further damage to the nerves after surgery. However, without complications, people with neurofibromatosis have a normal life expectancy and can lead normal lives.
Prevention & Follow Up
Children with neurofibromatosis are followed-up annually.