Review Question - QID 214058

This patient has clinical and radiographic findings suggestive of neurofibromatosis type 1 (NF1). NF1 is an autosomal dominant disorder of neural crest origin.

Patients with NF1, also known as von Recklinghausen disease, often have several unique clinical and radiographic findings. The diagnosis of NF1 is established by the consensus criteria set by the National Institutes of Health which requires a patient have two or more of the following signs: >6 café-au-lait spots (at least 15 mm in adults, and 5 mm in children), >2 neurofibromas of any type or one plexiform neurofibroma, freckling in the axillary or inguinal regions, optic glioma, >2 Lisch nodules (iris hamartomas), a distinctive bony lesion such as congenital tibial pseudarthrosis or dystrophic scoliosis, or a first-degree relative with NF1. Additionally, the presence of anterolateral tibial bowing is highly suggestive of NF1.

Crawford et al. reviewed NF1 and identified it as one of the most common human single-gene disorders. They report orthopedic manifestations that include spinal deformity, congenital tibial dysplasia (congenital bowing and pseudarthrosis), and disorders of excessive bone and soft-tissue growth. They conclude that the condition can be conclusively diagnosed when two of seven criteria established by the National Institutes of Health Consensus Development Conference are met.

Feldman et al. reviewed the orthopedic manifestions of NF1. They report that this autosomal dominant disease has orthopedic manifestions including scoliosis (dystrophic and nondystrophic), congenital pseudarthrosis of the tibia, problems related to soft-tissue tumors, and metabolic bone disease. They conclude that management of tibial pseudoarthrosis is challenging and failure to achieve union leads to high rates of refracture.

Figure A is the AP radiograph of the right lower leg which reveals anterolateral tibial bowing with pseudoarthrosis of the tibia. Figure B is the corresponding lateral radiograph of the right lower leg. Figure C is the clinical image of a Lisch nodule (iris hamartomas). Illustration A is a clinical image of anterolateral tibial bowing. Illustration B is a clinical image of axillary freckling. Illustration C is an optic nerve glioma.

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Answers 2-5: NF1 is an autosomal dominant disorder of neural crest origin