Koebner Phenomenon: Café-au-Lait Spots Developing after a Secondary-Degree Burn in a Patient with Neurofibromatosis Type 1

An 18-year-old woman with an established history of neurofibromatosis type 1 (NF-1) presented for her 1-year dermatologic follow-up. Physical examination revealed two subcutaneous nodules on her right arm, axillary freckling, scattered café-au-lait macules (CALMs) on the trunk, and a 12 cm × 17 cm hyperpigmented rectangular region on her right flank (Figure 1). The pigmented patch contained numerous new CALMs that were morphologically consistent with CALMs identified on prior examinations; neither the patch nor the CALMs within it were present at prior examinations. Interestingly, the appearance of the patch and associated CALMs was preceded by a rectangular-shaped, second-degree thermal burn. On further questioning, the patient revealed that she had burned herself with hot water 4 months prior to her presentation in clinic, and noted the development of multiple CALMs within the skin area of her prior burn approximately 4 weeks after the incident. Of note, her left flank had sparsely scattered CALMs, which was consistent with her prior skin examinations (Figure 2). A depigmenting cream was to be applied to the rectangular pigmented patch; unfortunately, post-inflammatory hyperpigmentation from the burn and the adjoining lesions resulting from the Koebner phenomenon continue to be refractory to treatment.