Neurofibromatosis 1 (NF1) is a multisystem disorder characterized by multiple café au lait macules, intertriginous freckling, multiple cutaneous neurofibromas, and learning disability or behavior problems. About half of people with NF1 have plexiform neurofibromas, but most are internal and not suspected clinically. Plexiform neurofibromas can cause pain, neurologic deficits, and abnormalities of involved or adjacent structures. Less common but potentially more serious manifestations include optic nerve and other central nervous system gliomas, malignant peripheral nerve sheath tumors, scoliosis, tibial dysplasia, vasculopathy, and gastrointestinal, endocrine, or pulmonary disease.

Spinal neurofibromatosis is an autosomal dominant disorder characterized by a high load of spinal tumors. These tumors may be asymptomatic or result in neurologic symptoms, including back pain, difficulty walking, and paresthesias. Spinal NF is considered to be a subtype of neurofibromatosis type I (NF1; 162200), which is an allelic disorder. Patients with spinal NF may or may not have the classic cutaneous cafe-au-lait pigmentary macules or ocular Lisch nodules typically observed in patients with classic NF1. Patients with spinal NF should be followed closely for spinal sequelae (summary by Burkitt Wright et al., 2013).

Approximately 5 to 20% of all patients with neurofibromatosis type I (162200) carry a heterozygous deletion of approximately 1.4 Mb involving the NF1 gene and contiguous genes lying in its flanking regions (Riva et al., 2000; Jenne et al., 2001), which is caused by nonallelic homologous recombination of NF1 repeats A and C (Dorschner et al., 2000). The 'NF1 microdeletion syndrome' is often characterized by a more severe phenotype than that observed in the majority of NF1 patients. In particular, patients with NF1 microdeletion often show variable facial dysmorphism, mental retardation, developmental delay, an excessive number of early-onset neurofibromas (Venturin et al., 2004), and an increased risk for malignant peripheral nerve sheath tumors (De Raedt et al., 2003).