Coexistence of Giant Congenital Melanocytic Nevus and Neurofibromatosis Type 1 among Child : A Rare Association

Abstract

Background: Giant congenital melanocytic nevus (GCMN) are rare pigmented lesions present at birth, often exceeding 20 cm in size, and may be associated with serious complications such as melanoma and neurocutaneous melanosis. Neurofibromatosis type 1 (NF1) is a common phakomatosis characterized by café-au-lait macules and neurofibromas. The coexistence of GCMN and NF1 is rare and may represent overlapping activation of the RAS/MAPK pathway. Case report: We report the case of a 5-year-old boy presenting with a bathing trunk–type GCMN involving the trunk, buttocks, and thighs, along with multiple smaller pigmented nevi. He also exhibited soft, mobile nodules on the lower back and pubic region, consistent with cutaneous and plexiform neurofibromas. Numerous café-au-lait macules were noted, but no axillary freckling. Ophthalmological, neurological, and radiological evaluations were normal. Histopathological examination confirmed congenital melanocytic nevus and neurofibromas. The diagnosis of NF1 was established based on NIH criteria. Discussion: This case illustrates a rare co-occurrence of GCMN and NF1. Although both conditions share a RAS pathway dysregulation, their combination is seldom reported. The association may increase the risk of melanoma or neurocutaneous melanosis, requiring long-term clinical and imaging surveillance. Conclusion: Recognizing the simultaneous presence of GCMN and NF1 is essential for early diagnosis, multidisciplinary management, and genetic counseling. This rare association highlights the importance of long-term surveillance to detect potential complications such as melanoma and neurocutaneous melanosis.