Phacomatosis Pigmentokeratotica

Phacomatosis spilosebacea: A new name for a distinctive binary genodermatosis

Phacomatosis pigmentokeratotica (PPK) is defined by the association of papular nevus spilus arranged in a flag-like pattern and sebaceous nevus following Blaschko's lines. A systematic search of the worldwide literature retrieved 95 well-established PPK cases. An additional 30 cases were excluded for a number of reasons. Based on this study, we propose to rename PPK phacomatosis spilosebacea (PSS). Mosaic mutations of the HRAS gene are the only proven cause of PSS. The extracutaneous abnormalities of PSS result from various degrees of intermingling of Schimmelpenning syndrome and papular nevus spilus syndrome. PSS seems to be a condition at particularly high risk of developing basal cell carcinoma, urogenital malignancies, and vitamin D-resistant hypophosphatemic rickets. Extracutaneous abnormalities were detected in approximately 75% of PSS cases.

Two Distinct Types of Speckled Lentiginous Nevi Characterized by Macular versus Papular Speckles

BACKGROUND

Speckled lentiginous nevus (SLN; synonym: nevus spilus) is a darkly spotted light-brown macule that mostly occurs as an isolated lesion of rather limited dimensions but sometimes may involve large areas of the body. So far, this skin disorder has been considered to represent one clinical entity.

OBJECTIVE

Because SLN is occasionally associated with complex birth defects such as phacomatosis pigmentovascularis, phacomatosis pigmentokeratotica, or SLN syndrome, we tested our idea that two different types of SLN may exist, each one associated with a particular syndrome.

METHODS

A review of case reports on SLN published during the years 1970-2004 was performed.

RESULTS

This evaluation of cases provided evidence that two different types of SLN exist, in the form of macular versus papular SLN, each one being related to a specific syndrome. Macular SLN is characterized by a tannish-brown background with darker flat speckles. The distribution of speckles is rather even and resembles a polka-dot pattern. Histopathologically, this type of SLN is characterized by what has been called a 'jentigo' pattern in the darker speckles and by some nests of melanocytes at the dermoepidermal junction at the tips of the papillae, whereas the background pigmentation shows the microscopical features of a lentigo. Papular SLN is characterized by a light-brown macule superimposed by multiple melanocytic nevi in the form of papules or nodules that show a more uneven distribution reminiscent of a star map. Small dark macules may likewise be present. Histopathologically, the papular component consists of dermal or compound melanocytic nevi. A separation of the two types of SLN is important because our analysis showed that macular SLN is a hallmark of a particular type of phacomatosis pigmentovascularis, whereas papular SLN is typically present in phacomatosis pigmentokeratotica as well as in SLN syndrome.

CONCLUSIONS

Macular SLN and papular SLN appear to be two distinct cutaneous entities. This dichotomy may turn out to be important when such nevi will be analyzed at the molecular level.