Acquired Dermal Melanocytosis on the Wrist

Abstract

A 50-year-old Japanese man had a blue-black patch on the dorsum of his right wrist. Light and electron microscopic study of the lesion revealed dermal melanocytes containing mature melanosomes, predominantly in the upper dermis. This case was diagnosed as acquired dermal melanocytosis confined to the right wrist.

Characteristics of Hori naevus: a prospective analysis

“…In this context, other than epidermal melanocyte migration as previously discussed, sun exposure and hormonal fluctuations in pregnancy possibly contribute to the reactivation of these latent melanocytes in the dermis. Exposure to the sun has been postulated to induce melanogenesis via the induction of tyrosinase activity by melanocyte‐stimulating hormone 7 …”

Studies of pigment transfer between Xenopus laevis melanophores and fibroblasts in vitro and in vivo1

“…However, in inflammatory skin disorders melanins can be transferred abnormally to the dermis in a process called pigmentary incontinence or dermal melanosis (Masu and Seiji, 1983). Melanocytes can also be abnormally located in the dermis in a condition called dermal melanocytosis (Kuniyuki, 1997). These cells synthesize melanin, but so far no studies have been performed which report transfer to keratinocytes or dermal cells.…”

Letter to the Editor

“…The other sites that have been mentioned in the literature are the extremities, the wrist and the dorsum of the hand 3,4 . The acral distribution of dermal melanocytosis has been reported very rarely 3,4 . In our patient, lesions started on the hand at 14 years of age, which progressed to involve the wrist and forearm.…”

“…Histologically, melasma can be differentiated by the presence of epidermal hypermelanosis with many dermal melanophages in the papillary dermis. The other sites that have been mentioned in the literature are the extremities, the wrist and the dorsum of the hand 3,4 . The acral distribution of dermal melanocytosis has been reported very rarely 3,4 .…”