Longterm digital monitoring in the diagnosis and management of congenital nevi of the nail apparatus showing pseudo-Hutchinson’s sign

Congenital nail apparatus nevi often show substantial enlarge -ment and wide involvement and greatly concern parents of a child as well as dermatologists. The differential diagnosis from melanoma is critical. The biopsy of the nail matrix is very traumatic and a fearful experience for a child. Therefore, a longterm careful follow-up with digital monitoring is very important and should be the first choice of management.Ronger et al. [1] reported that only three cases of mel-anoma showed micro-Hutchinson’s sign in 148 cases of melanonychia. However, similar findings are also observed in congenital nevus of the nail apparatus. We report three cases of congenital or early-onset nevus of the nail appara-tus with minute periungual regular pigmentation found on dermoscopy.We used the terms, “Hutchinson’s sign” and “pseudo-Hutchinson’s sign” based on the original descriptions [2, 3]. Baran and Kechijian [3] originally defined the term, pseudo-Hutchinson’s sign, for three conditions, including 1) benign pigmentation of the nailfolds, 2) pigmentation of the nailfolds due to malignant but non-melanoma tumors, 3) pigmentation seen through translucent nailfolds.


Introduction
Congenital nail apparatus nevi often show substantial enlargement and wide involvement and greatly concern parents of a child as well as dermatologists. The differential diagnosis from melanoma is critical. The biopsy of the nail matrix is very traumatic and a fearful experience for a child. Therefore, a longterm careful follow-up with digital monitoring is very important and should be the first choice of management.
Ronger et al. [1] reported that only three cases of melanoma showed micro-Hutchinson's sign in 148 cases of melanonychia. However, similar findings are also observed in congenital nevus of the nail apparatus. We report three cases of congenital or early-onset nevus of the nail apparatus with minute periungual regular pigmentation found on dermoscopy.
We used the terms, "Hutchinson's sign" and "pseudo-Hutchinson's sign" based on the original descriptions [2,3]. Baran and Kechijian [3] originally defined the term, pseudo-Hutchinson's sign, for three conditions, including 1) benign pigmentation of the nailfolds, 2) pigmentation of the nailfolds due to malignant but non-melanoma tumors, 3) pigmentation seen through translucent nailfolds.

Case 1
A 10-year-old Japanese boy presented with pigmentation of the nail of the right ring finger. The lesion was noticed at birth. Physical examination showed melanonychia of the fingernail. He had been followed up for eight years.

Case 2
An 11-year-old Japanese boy presented with pigmentation of the nail of the right middle finger. The lesion was noticed when he was 7 years old. Physical examination showed melanonychia of the fingernail. He had been followed up for three years. Dermoscopy showed regular dark brown lines and a brown band (Figure 2A-C). The brown background band slightly widened compared with previous dermoscopy results, however, the dark brown lines on the band were gradually decreasing. There were also blue-gray dots along the brown lines, which also seemed to be gradually decreasing. There was a regular minute fibrillar pattern on the proximal nailfold, which was not noticed at the clinical examination. A possibility of melanoma has been ruled out because of scarce change through the follow-up for three years.  Although congenital nevus often shows periungual pigmentation, resulting in increased concern on the part of the clinician and therefore necessitating biopsy, we would like to

Discussion
The brown-black periungual pigmentation seen in melanoma is known and described as Hutchinson's sign [2]. However, such periungual pigmentation could be found not only in melanoma but also in various benign conditions such as congenital nevus, Laugier-Hunziker-Baran syndrome, subungual hematoma, and nonmelanoma skin cancer such as Bowen's disease, or in the pigmentation observable through the translucent nailfolds [3]. Ronger et al. described the minute periungual pigmentation in melanomas as micro-Hutchinson's sign, which is difficult to find with the naked eye but could be observed on dermoscopy. They reported that micro-Hutchinson's sign was observed only in three cases of nail apparatus melanoma, but not in nevi from 148 melanonychia cases [1].
As we noted similar minute periungual pigmentation in congenital nevus of the nail apparatus, we presented three such cases. Our follow-up observation revealed that congenital or early-onset nevus of the nail apparatus also showed minute periungual pigmentation. Therefore, we described and named them as "pseudo-micro-Hutchinson's sign." However, as this term seems to describe several different conditions, we  propose that a biopsy is not necessarily applicable. Instead, if dermoscopic features are regular in lines, longterm followup is important to rule out melanoma. In our opinion, all the nevi in children would increase in size for certain periods at the beginning and then decrease in pigmentation. One of the signs for regression is the "neumatic notation"-like blue-gray dots, as Murata and Kumano reported [4]. When this sign is observed, we would wait and expect that the nail pigmentation might disappear. Therefore, we think that it is more important to follow up on the changes of the nevus rather than to biopsy it. A biopsy of nail matrix would result in permanent nail deformity; additionally, the procedure of a biopsy is a fearful experience for children in this age.
The blue-gray dots are a sign of regression of melanonychia in children [4]. This finding would correspond to transepithelial elimination of melanin or apoptotic melanocytes in the nail plate. As originally described by Murata and Kumano, these dots appear like the neumatic notation of the Gregorian chant ( Figure 4). Knowledge about this feature is