Dermatomal patterns and congenital melanocytic nevi distribution in the head, neck, trunk, back, and limbs

Congenital melanocytic nevi (CMN) are benign melanocyte nevi that appear at birth and can be found in the dermis, epidermis, or both layers of the skin. These CMN are caused by mutation in the melanocyte’s cells. This mutation leads to their lacking dendrites and causes CMN. This study aimed to investigate the correlation between CMN distribution and dermatomes. Clinical photographs of CMN (>1.5cm) from a quaternary hospital in Durban, South Africa, were analyzed. Two investigators examined the clinical photographs to evaluate the size and dermatomes covered by the nevi (n=31). The observed CMN distribution was transposed onto a dermatome template, and the prevalence among dermatomes was compared. The results showed a higher preference for T10 (58.1%) and similar patterns in T11 (54.8%) and T12 (51.6%). Facial dermatomes V1 and V2 (54.8%) were mostly affected with the areas of zygomaticofacial, zygomaticotemporal, and supraorbital nerves in the cervical region C5 (32.3%) and lumbar L1 (41.9%) were notably affected. Varied CMN patterns were observed in the head and neck region, emphasizing the complexity of CMN distribution. The study enhances our understanding of CMN presentation, shedding light on the potential for CMN to follow a dermatomal distribution, with CMN often mostly found in the trunk region around T10, T11, and T12. V1 and V2 dermatomes in the face with zygomaticotemporal, zygomaticofacial, and supraorbital branches were mostly affected, suggesting embryological influences during the maxillary process fusion.