Rare Case of Phakomatosis Pigmentokeratotica reported in NEJM

Akiharu Kubo, at Keio University School of Medicine, Tokyo, Japan and Dr Daisuke Yamada, at University of Tokyo Graduate School of Medicine, Tokyo, Japan has reported a rare case of Phakomatosis Pigmentokeratotica. The case has appeared in the New England Journal of Medicine.

Phacomatosis pigmentokeratotica (PPK), described in 1996, is characterized by speckled lentiginous nevus (SLN) in association with an organoid nevus showing sebaceous differentiation and extracutaneous neurologic, ophthalmologic, and musculoskeletal abnormalities.Phacomatosis pigmentokeratotica is a rare and distinct variant of the epidermal naevus syndrome, first described by Happle et al.³. It comprises the association of an organoid (epidermal) naevus with sebaceous differentiation and a speckled lentiginous naevus^4,5 arranged in a checkerboard pattern. There are often other anomalies, most common neurological or skeletal, such as hemiatrophy, dysaesthesia and hyperhidrosis in a segmental pattern, mild mental retardation, seizures, deafness, ptosis and strabismus⁶.

A 37-year-old man was referred to the dermatology clinic for evaluation of skin lesions that had been present since birth. On physical examination, two types of lesions were observed: brownish hyperkeratotic papules following Blaschko’s lines (arrowhead) and pigmented papules distributed in a segmental pattern (arrow).

Biopsy specimens obtained from the right arm and the left side of the neck indicated that the hyperkeratotic papules were sebaceous nevi and the pigmented papules intradermal melanocytic nevi. An additional biopsy specimen obtained from a lesion on the right forearm (not shown) revealed squamous-cell carcinoma. Genetic testing was performed on both types of nevi and revealed the same HRAS c.181C→A (p.Gln61Lys) mosaic mutation in both samples.

A diagnosis of phakomatosis pigmentokeratotica was made. Owing to the increased risk of cancer involving the skin and other organs that is associated with this rare disorder, regular surveillance and cancer screening are important. The patient underwent complete excision of the squamous-cell carcinoma. He remains under regular surveillance.