Pseudoarthrosis of the Ulna in Neurofibromatosis Type I

Abstract

A 4-year-old female presented to the neurofibromatosis clinic with a congenital anomaly of the right forearm, numerous café au lait spots, axillary and inguinal freckling, and several soft, flesh-colored papules and nodules on the back consistent with neurofibromas (Figure, A). A prior magnetic resonance imaging study of the brain revealed optic pathway gliomas, for which she was undergoing chemotherapy. Family history was significant for a diagnosis of neurofibromatosis type 1 (NF1) in the mother and maternal grandmother. Radiographic images of the right arm were diagnostic of pseudoarthrosis of the ulna (Figure, B). The patient met clinical diagnostic criteria for NF1 based on café au lait spots, intertriginous freckling, neurofibromas, optic glioma, and a positive family history. 1,2 In patients who present with congenital long bone pseudoarthrosis, 50%-80% have an underlying diagnosis of NF1. The prevalence of pseudoarthrosis among patients with NF1 is 5%. 3 Pseudoarthrosis occurs when there is nonunion of bone fragments at the site of a long bone fracture forming a false joint. This can occur in NF1 from bone dysplasia causing impaired healing. 4 The most common location for this to occur is the tibia. Pseudoarthrosis of the forearm is rare, usually involving the ulna. 5 Management can be complex and an orthopedic surgeon should be consulted. Consensus guidelines for the treatment of pseudoarthrosis by the Children's Tumor Foundation include bone fixation to appropriately stabilize the bone, debridement of the fibrous pseudoarthrosis tissue between bone segments, optimizing bone repair by creating healthy vascular beds to promote osteogenesis, and preventing recurrence of fracture. 6 Owing to the strong association with NF1, any child presenting with congenital pseudoarthrosis of a long bone should undergo further clinical evaluation for NF1. ■