Phacomatosis pigmentokeratotica without extracutaneous abnormalities: 12-year follow-up

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.

The first case of Chinese phacomatosis pigmentokeratotica diagnosed by a missense HRAS mosaicism

Phacomatosis pigmentokeratotica (PPK) is a rare epidermal nevus (EN) syndrome, featured by co-occurrence of speckled lentiginous nevus (SLN) and nevus sebaceous (NS). The underlying mechanism has not been clarified. Pathogenic mutations in HRAS, KRAS and BRAF gene are recently recognized as the genetic cause of PPK. Here we present a case of Chinese PPK with a mosaic mutation in HRAS gene. Physical examination of the 4-year-old male proband showed NS locating on the scalp, with EN and SLN on trunk and extremities. Except congenital fundus vascular tortuosity, no evidence of extracutaneous abnormalities was found in this case. A rare heterozygous missense c. 181 C>A mosaic mutation in HRAS was identified in samples from NS, EN and pigmented nevus using next-generation sequencing and Sanger sequencing. Meanwhile, no mutation was found in the non-lesion skin, hair follicle, or blood DNA. Recent breakthrough in clinical manifestation, genetic mutation and prognosis of PPK is also reviewed.