A 44-year-old Hispanic man has neurofibromatosis type 1 (NF-1). He has typical features of NF-1, including eight café-au-lait spots, axillary freckling, and neurofibromas all over his body (Figures 245-1, 245-2, 245-3, 245-4). He states that he is used to having the neurofibromas and they do not currently affect his work or life. He is happily married but never had children. No intervention is necessary at this time other than recommending yearly visits to his family physician and ophthalmologist.
A 44-year-old Hispanic man with neurofibromatosis type 1 showing all the typical findings including neurofibromas, café-au-lait spots, and axillary freckling. (Reproduced with permission from Richard P. Usatine, MD.)
Close-up of neurofibromas on the back of the man in Figure 234-1. These are soft and round. (Reproduced with permission from Richard P. Usatine, MD.)
Large café-au-lait spot on the back of the man in Figure 234-1. Café-au-lait spots are ovoid hyperpigmented macules, 10 to 40 mm in diameter, with smooth borders. (Reproduced with permission from Richard P. Usatine, MD.)
Close-up of axillary freckling (Crow sign) with large café-au-lait spot on arm. (Reproduced with permission from Richard P. Usatine, MD.)
NF-1, formerly known as von Recklinghausen disease, is a common autosomal dominant disorder that predisposes to tumor formation. Café-au-lait macules are often the first clinical sign. Other clinical signs include neurofibromas, axillary or inguinal freckling, optic gliomas, Lisch nodules (iris hamartomas), and sphenoid bone dysplasia. Treatment is early recognition and monitoring for complications such as cognitive dysfunction, scoliosis or other orthopedic problems, tumor pressure on vital structures, or malignant transformation.
NF-1 is relatively common—Birth incidence is 1 in 3000 and prevalence in the general population is 1 in 5000.1
Autosomal-dominant inheritance; however, up to 50% of cases are sporadic1; likelihood of sporadic cases increases with advanced paternal age.
Diagnosis is typically made during childhood.
Segmental NF-1, a condition in which lesions are limited to part of the body, is less common, with an incidence of 1 in 36,000 to 40,000.2
ETIOLOGY AND PATHOPHYSIOLOGY
Mutations in the NF1 gene (on the long arm of chromosome 17) result in loss of function of neurofibromin, which helps keep protooncogene ras (which increases tumorigenesis) in an inactive form.
Loss of neurofibromin results in increased protooncogene ras activity in neurocutaneous tissues, leading to tumorigenesis.1
Segmental NF-1 is caused by somatic mosaicism due to ...