Neurofibromatosis(NF) is an autosomal dominant disease characterized by disordered growth of ectodermal tissues, and is part of a group of disorders called Phakomatoses (neurocutaneous syndrome).
NF is divided in two Types:
Neurofibromatosis 1(NF1) is characterized by spots of increased skin pigmentation(café au lait spots), combined with peripheral nerve tumors and a variety of others dysplastic abnormalities of the skin, nervous system, bones, endocrine organs and blood vessels.
Etiology
The reponsible gene is located on the long arm of chromosome 17
Epidemiology
Its incidence is 1 per 3.000 births and present in about 30 persons per 10.000 population. It is inherited as an autosomal dominant trait, but about 50 percent of cases arise as mutations.
Pathology
The peripheral nerve tumors of two types, schwannomas and neurofibromas. Both types of tumor occasionally become malignant.
Clinical Manifestations
The pigmented spots are irregular in shape with relatively even borders, vary in size, and are of brownish coffe color(café au lait). They are most proeminent over the trunk, in the axilla(axillary freckles), and about the pelve.
The tumors are usually multiple and vary in size from minute lesions to large tumors. The majority are smoothly rounded or lobulated, and can sometimes be seen or felt along the course of peripheral nerves. Often they sink into the subcutaneous fat on gentle pressure. They are also more frequent over the trunk.
Plexiform neurofibromas may grow a lot, leading to grotesque overgrowth of soft tissue and bone in a limb or around the orbit. Below is shown a photo of a patient with NF1.
Tumors of the spinal nerve roots may compress the spinal cord and at the same time extend though the intervertebral foramens to form a large mass in the posterior mediastinum(Dumbbell tumors).
Stenosis of the aqueduct of Sylvius with obstructive hydrocephalus is at times observed in NF1. There is also an association of vascular stenoses(renal,cerebral or pulmonic) and NF1.
Diagnosis
The diagnosis of NF1 is not a difficult one beeing evident on clinical grounds. In Table 1 are listed Neurofibromatosis' diagnostic criteria.
| A patient meeting two or more of the following criteria can be diagnosed as suffering from NF 1 | |
|---|---|
| 1 - Neurofibromas - Two or more, or one plexiform neurofibroma 2 - Café-au-lait macules - Six or more measuring 1,5 cm in their greatest dimension 3 - Freckling - In the axillary or inguinal areas 4 - Optic glioma 5 - Iris hamartomas(Lisch nodules) - Two or more 6 - Sphenoid dysplasia or thinning of the cortex of the long bones 7 - First-degree relative |
In difficult cases biopsy of a neurofibroma can be diagnostic. Magnetic resonance and computed tomography are important in the diagnosis of spinal nerve root tumors, intracranial tumors and hamartomas.
Treatment
There is no treatment for the disease, but small cutaneous or subcutaneous neurofibromas can be removed if they are painful.
Neurofibromatosis 2(NF2) is an autosomal dominant disorder localized to chromosome 22(long arm) and characterized by bilateral acoustic neurofibromas and often other intracranial tumors such as meningiomas and ependymomas.
This disease has a prevalence of 0.1 per 100.000 and family members at risk should be screene regularly with hearing tests and brain stem auditory evoked responses.
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