Researchers Say Evidence Points to Need for Terminology Change in Axillary and Inguinal Lentiginosis in Neurofibromatosis

Image courtesy of Derm Net

The dermatology world should consider a terminology change from axillary and inguinal freckling in neurofibromatosis (NF) type 1, or "freckling," to axillary and inguinal lentiginosis, according to data presented in a poster at the Maui Derm Hawaii 2024 conference in Wailea, Hawaii.¹

Pigmented macules found in the axillae and inguinal areas of individuals with NF type 1, smaller than typical café-au-lait macules (CALM), are commonly referred to as "freckling." This phenomenon is not exclusive to NF type 1, as similar pigmentation is observed in genetic disorders affecting the RAS/MAPK pathway, leading to the use of the term "lentiginosis" in some instances.²

A study published by researchers from Pyeongchon, Korea, delved into a histological examination of facial freckles, solar lentigo, and skin fold freckling to determine the nature of these pigmented lesions.

In their research, a total of 7 cases were selected for biopsy, comprising 5 cases of skin fold freckling (3 axillary freckling and 2 inguinal freckling), one case of solar lentigo (a 70-year-old patient), and one case of facial freckle (a 27-year-old -atient). The biopsies were stained using hematoxylin–eosin and Fontana–Masson to visualize the histological features.

Histological analysis of facial freckles revealed an increased melanin concentration in the epidermal basal layer without melanocyte hyperplasia. Furthermore, skin fold freckling displayed diffuse increased basal pigmentation, an elevated number of melanocytes, moderate elongation of rete ridges in the epidermis, and mild dermal inflammatory cell infiltration with a few melanophages, resembling the characteristics of solar lentigo.

The findings from clinical, histological, and genetic perspectives suggest a reevaluation of the terminology used for axillary and inguinal pigmentation in NF type 1, according to authors. Based on the evidence presented, Baek et al proposed that the term "freckling" be replaced with "lentiginosis" for axillary and inguinal pigmented macules in individuals with NF type 1.

References

1. Baek JO, Jeong DI, Kim M, Kim TW, Kim YR, Huh H. Axillary and inguinal lentiginosis (not freckles) in neurofibromatosis. Poster presented at: Maui Derm Hawaii 2024; January 22-26, 2024; Wailea, HI.
2. Boyd KP, Korf BR, Theos A. Neurofibromatosis type 1. J Am Acad Dermatol. 2009;61(1):1-16. doi:10.1016/j.jaad.2008.12.051