Neurofibromatosis Type 1 (NF1) is an autosomal dominant disorder effecting the protein neurofibromin on chromosome 17. This is tumor supressor gene that inhibits the p21 ras oncoprotein. Although autosomal dominant, 50% of NF1 arises as a new mutation in a patient without a family history.
The diagnostic criteria for NF1 include having at least two of the following:
1. At least 6 cafe au lait spots
2. At least 2 neurofibromas
3. Freckles in the axillary or inguinal regions
4. Optic gliomas
5. At least 2 Lisch nodules
6. Characteristic bone lesions such as sphenoid dysplasia or thinning of the cortex of long bones
7. A first degree relative (parent, sibling, child) with the disease.
There are many clinical features of NF1 and a wide range of manifestations thus affecting prognosis.
Some complications include learning disabilities and decreased IQ levels, hypertension due to reno-vascular abnormalities, facial bone deformities, and scoliosis.
Cutaneous features include cafe au lait spots (which appear as large flat dark macules), freckling in areas that do not normally freckle (such as the armpit or groin area), and also neurofibromas (which are firm, skin colored nodules that appear anywhere on the body).
Nuerofibromas are not only cutaneous however. There are subcutaneous forms and plexiform forms. The plexiform type can progress to a malignant condition further discussed below.
The central nervous system is effected with NF1 as well. There is an increased incidence of epilepsy, along with optic gliomas. Optic gliomas present as a change in vision or blindness and typically occur in those under 6 years of age. It is important to screen for these annually. Astrocytomas and brainstem gliomas (both are brain tumors) are more common in NF1 as well.
By far the most serious complication is a malignant peripheral nerve sheath tumor (MPNST), which arises from plexiform neurofibromas. Plexiform neurofibromas progress to MPNSTs about 8-12 percent of the time.
MPNSTs present as edema, or swelling, in an extremity with difficulty moving. This swelling is often painless but soreness localized to the area of the tumor is also common. Prognosis, even when complete resection is possible, is dismal.
MRI screening for this malignant transformation has been studied, but it has unfortunately not yielded promising results. Instead, it is important for patients to be aware of the symptoms. If chronic pain was present, any change or difference should be investigated.
NF1 is a serious disease with many clinical features. There is not a cure, however many of the treatment and screening regimens can help decrease the morbidity and mortality related to this disease.