Phakomatosis Pigmentokeratotica
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.
