Neurofibromatosis (overview) Q85.0

Group of hereditary, autosomal-dominantly inherited or spontaneously mutated neuroectodermal systemic diseases in which 8 types can currently be distinguished from a clinical and genetic point of view (see Table 1). The main symptom is neurofibroma.

• Type I Peripheral neurofibromatosis, also known as classic or cutaneous NF, 85% of all cases. Autosomal dominant inherited defect of the NFI gene (neurofibromatosis-1 gene; gene locus: 17q11.2). It is characterized by cafe-au-lait spots and visible neurofibromas.
• Type II Central neurofibromatosis, uni- or bilateral acoustic neuromas (hearing loss often as first symptom at 20-30 years of age); cafe-au-lait spots only in about 50% of cases, no Lisch nodules. This form of neurofibromatosis is caused by an autosomal-dominantly inherited mutation of both alleles in the NFII gene (neurofibromatosis-2 gene; gene locus: 22q12.2) with consecutive disruption of the expression of the tumor suppressor protein Merlin (acronym for Moesin-Ezrin-Radixin like protein) also known as Schwannomin (see below).
• Type III Central-peripheral neurofibromatosis (palmo-plantar neurofibromatosis)
• Type IV Atypical neurofibromatosis (heterogeneous group). Autosomal-dominantly inherited inversions on gene locus 12q21-12q24.2.
• Type V Segmental neurofibromatosis, very rare, somatic mutation (see also association with Cobb syndrome)
• Type VI Familial intestinal neurofibromatosis (multiple café-au-lait spots without neurofibromas)
• Type VII Neurofibromatosis-pheochromocytoma-duodenal carcinoid system (NPDC)
• Type VIII neurofibromatosis-Noonan syndrome (syn. Watson syndrome), complex form of peripheral neurofibromatosis (NF type I) with the clinical phenotype of Noonan syndrome (short stature, ptosis, midface hypoplasia, pterygium colli, learning disability and muscle hypotonia). Autosomal dominant inherited defect of the NF1 gene (neurofibromatosis Noonan syndrome gene; gene locus: 17q11.2) with consecutive defect of neurofibromin (see NF1 gene below)

Incidence: 30-40 patients/100,000 inhabitants; about 1 child affected/2,500-3,300 births. In about 50% of cases a new mutation is probable.

Pigmentation spots appear from birth or in childhood, tumours mainly during puberty. Men are more frequently affected than women.

The clinical picture varies according to the expression type of neurofibromatosis (see Tab).

• Pigmentary spots: café-au-lait spots, axillary freckling, patchy pigmentation of the oral mucosa.
• Nevi: melanocytic nevi, hemangiomas and lymphangiomas, lentigines, nevi spili.
• Single or numerous, pea-sized or monstrous, skin-colored to bluish, broad or pedunculated papules or nodules (neurofibromas), possibly with wrinkling or as dewlap-like structures, cutis laxa. Bell button phenomenon: Hernia-like subcutaneous tumors protruding through the skin can be pushed back with a finger.
• Skeleton: Kyphoscoliosis, pointed foot, cystic extensions, thickenings and lengthenings on long bones.
• Eyes: Lisch nodules, characteristic in NF1, do not occur in NF2, NF3, and NF4. For the diagnosis of NF1, see. Table 2.

According to the neurofibroma.

• At least 6 café-au-lait stains (before puberty: > than 0.5 cm in diameter, then > 1.5 cm in diameter)
• Axillary or inguinal pigmentation (axillary freckling)
• At least 2 neurofibromas or 1 plexiform neurofibroma.
• A first-degree relative with peripheral neurofibromatosis.
• At least 2 Lisch nodules.
• Bone lesions.

• Dermatologically relevant are especially café-au-lait stains and neurofibromas. Cosmetically disturbing or painful, rapidly growing tumours are excised. Important in the treatment is the regular comprehensive examination of the patient and his relatives at least once a year in order to detect the development of new tumours early! Otherwise genetic counselling, prenatal diagnostics is theoretically possible for the peripheral NF and the central NF (type II).

• Remember! Regular neurological, ophthalmological and ENT medical examinations are required!

Quoad vitam cheap. Increase of tumours during life in number and size. In 5% sarcomatous degeneration with metastasis ( neurofibrosarcoma).

Symptoms of neurofibromatosis of the peripheral type (type I)

According to the Knudson hypothesis, type II neurofibromatosis requires the mutation of both alleles of the NF-2 gene in order to develop tumours. This is the case with autosomal dominant inheritance.

If only 1 allele is affected, either due to a germ cell mutation or a de novo mutation ("first hit"), tumour development can occur in the course of life from cells that lose the physiological function of the remaining, normal(wild-type) NF2 allele ("second hit").

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