Neurofibromatosis Type 1

Neurofibromatosis 1 (NF1) is a common, inherited autosomal dominant disease

The birth incidence is between 1 in 2,500 and 1 in 3,000, with about half being the first in their families to be affected.

Diagnostic criteria are that you need two or more of the following:

  • 6 or more cafe au lait macules (>0.5 cm in children and 1.5cm in adults)
  • 2 or more cutaneous/subcutaneous neurofibromas or 1 plexiform neurofibroma
  • axillary or groin freckling
  • optic pathway glioma
  • 2 or more Lisch nodules
  • bony dysplasia (sphenoid wing dysplasia, bowing of long bone +/- pseudarthrosis
  • parent or child with NF1

Patients with NF1 are at risk of a number of problems including optic pathway gliomas, CNS tumours, hypertension and congenital heart disease.

Orthopaedic problems include:

  • bowing of long bones +/- pseudarthrosis
  • scoliosis
  • osteoporosis
Oncological problems include:
  • benign tumours (neurofibroma, glomus tumours)
  • malignant tumours (10% lifetime risk of malignant change in plexiform neurofibromas (to malignant peripheral nerve sheath tumour),  optic pathway gliomas, cerebral gliomas,  phaeochromocytoma, rhabdomyosarcoma, juvenile myelomonocytic leukaemia, breast cancer in women)
Specialist neurofibromatosis clinics do exist but are few in number.
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Maffucci syndrome

Maffucci syndrome is a rare, non-inherited abnormality characterised by multiple enchondromas, bone deformity and vascular (occasionally lymphatic) malformations. The genetic defect is unknown. Ollier’s disease is a related condition in which there are multiple enchondromas, but no vascular malformations.

Enchondromas classically occur in the long bones and in the hands and feet, although involvement of the skull, ribs and vertebrae are described. The vascular malformations often appear as soft tissue masses with a bluish tinge in the skin, and are often partially calcified on x-ray.

The diagnosis is made clinically as there is no specific laboratory test, and patients may come to diagnosis at any age, depending on the severity of the condition.

The risk of malignancy is higher than in Ollier’s disease: the major concern is around the degeneration of enchondromas to central chondrosarcomas, but there can be associated malignancies including brain tumours and it is these which are possibly more likely to be life threatening. As with other rare syndromes estimating the absolute risk of malignancy is difficult: one study of seven patients reported that malignant change was a “certainty”, but this was a small study likely subject to referral bias. There appears to be a consensus that life expectancy is relatively normal.

Treatment tends to be symptomatic: large enchondromas may need curettage, particularly where hand function is impaired. Patients are followed for changes in symptoms or in the size of their enchondromas.

For an overview of enchondromatosis syndromes look at Pansuriya’s article.

The Orphanet entry for Maffucci syndrome can be found here.