Neurofibromatosis type 1
Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder caused by pathogenic variants of the NF1 gene on chromosome 17, which encodes neurofibromin.
Clinical features
Important manifestations include:
- café-au-lait macules
- axillary or inguinal freckling
- cutaneous or plexiform neurofibromas
- Lisch nodules / ocular manifestations
- optic pathway glioma
- distinctive osseous lesions
- first-degree family history or confirmed pathogenic NF1 variant
Orthopaedic manifestations
Spine
- scoliosis
- short, sharp dystrophic curves may occur
- vertebral scalloping, rib pencilling and foraminal enlargement may be seen
- dystrophic curves have a higher risk of progression
Long bones
- anterolateral bowing of the tibia
- congenital tibial pseudarthrosis
- limb-length discrepancy or overgrowth in some patients
Neurofibromas
Neurofibromas may be cutaneous, subcutaneous or plexiform. Plexiform neurofibromas are strongly associated with NF1 and may cause deformity, pain or neurological compromise.
Malignant transformation
New persistent pain, rapid growth, neurological deficit or change in consistency of a plexiform neurofibroma should raise concern for malignant peripheral nerve sheath tumour.
Management
Management is multidisciplinary. Orthopaedic treatment is directed at progressive spinal deformity, pseudarthrosis, limb deformity and symptomatic lesions.