Diagnosis of Neurofibromatosis
Family history, physical examination for clinical signs of the disease (e.g., multiple cutaneous and subcutaneous lesions), and magnetic resonance imaging (MRI) are used to diagnose neurofibromatosis. Diagnosis can be confirmed through genetic testing.
Physical Examination to Diagnose Neurofibromatosis
Six or more flat areas of hyperpigmentation on the skin (cafe au lait spots) are the most common clinical sign of NF. These spots usually appear by 2 years of age and increase in number over time. They are tan in light-skinned people, darker than surrounding skin in dark-skinned people, and they usually darken with age.
Small hyperpigmented spots that are difficult to distinguish from freckles may appear on the skin. Freckling usually occurs in areas of skin exposed to sun, but NF may cause freckling in other areas, including the armpit (axilla) and the groin.
Cutaneous tumors caused by NF often can be pressed into the skin manually, leaving a vacant space under the skin that may remain for some time (called buttonholing). Buttonholing distinguishes NF tumors from benign fatty tumors unrelated to NF (lipomas).
An eye specialist (ophthalmologist) may examine the eyes with a slit-lamp microscope to detect benign lesions on the iris (Lisch nodules), which may be caused by optic gliomas.
Magnetic resonance imaging (MRI scan) of the brain and spine may be used to detect tumors caused by neurofibromatosis (e.g., optic gliomas, vestibulocochlear nerve tumors, tumors of the spinal canal) and schwannomas. If multiple schwannomas are detected, high quality MRI of the base of the brain is performed to rule out Type 2 NF and diagnose schwannomatosis.
Tumors of the vestibulocochlear nerve that are detected by MRI may be evaluated using audiometry tests. These tests evaluate hearing and help to determine nerve function and detect tumor changes (e.g., growth).
Genetic Testing to Diagnose Neurofibromatosis
Genetic testing (e.g., gene linkage, mutation analysis) detects neurofibromatosis in about 90 percent of cases. These blood tests can be used to confirm diagnosis by identifying genetic abnormalities, to provide early detection for people with a family history of the disease who do not have symptoms, and to determine the risk for passing the disease to offspring.