Dermatopathologic evaluation of the tissue sample indicated that the lesion was a neurofibroma, and clinical correlation fine-tuned the diagnosis to segmental neurofibromatosis (NF). The diagnosis of segmental NF is clinical, with biopsy to confirm that the lesions are neurofibromas. Segmental NF is a mosaic form of neurofibromatosis type 1 (NF1) that results from a postzygotic mutation of the NF1 gene. While NF1 is a relatively common neurocutaneous disorder that occurs with a frequency of 1 in 3000, segmental NF is uncommon, with an estimated prevalence of 1 in 40,000.
NF1 often follows an autosomal dominant inheritance pattern, although up to 50% of patients with NF1 arise de novo from spontaneous mutations. NF1 is characterized by multiple café-au-lait macules, axillary freckling, neurofibromas, and Lisch nodules (pigmented iris hamartomas). Systemic findings associated with NF1 include malignant peripheral nerve sheath tumors, optic gliomas, and vasculopathy. While patients with segmental NF may exhibit some of these same findings, the distribution of the neurofibromas is often limited to a single dermatome. Additionally, patients with segmental NF typically do not exhibit extracutaneous lesions, systemic involvement, or a family history of NF. Segmental NF treatment typically focuses on symptomatic management or cosmetic concerns.
This patient did not have any of the systemic complications that occasionally occur with segmental NF, so no medical treatment was required. The patient was advised that cutaneous and subcutaneous neurofibromas do not require removal unless there is pain, bleeding, disfigurement, or signs of malignant transformation. The patient was not interested in removal of the nodules for cosmetic reasons, so he was encouraged to seek follow-up care, as needed.
This case was adapted from: Laurent KJ, Beachkofsky TM, Loyd A, et al. Segmental distribution of nodules on trunk. J Fam Pract. 2017;66: 765-767.