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Nevus psiloliparus: A Distinct Fatty Tissue Nevus

Background: Encephalocraniocutaneous lipomatosis is usually associated with a peculiar type of fatty tissue nevus which represents a smoothly surfaced and hairless lesion involving the scalp. This disorder has so far not been recognized as a cutaneous entity. Objective: The purpose of this article is to describe the characteristic features of this nevus and to give it a name. Method: From the study of two cases and from a review of the literature we delineate the clinical and histopathological criteria of this disorder for which we propose the term ‘nevus psiloliparus’. This name is derived from the Greek words psilós = hairless and liparós = fatty, and describes the two most characteristic features of the disorder. Results: A comprehensive comparison shows that nevus psiloliparus can be distinguished from other types of fatty tissue nevi by clinical criteria such as localization on the scalp, a flat smooth surface and absence of hair follicles, by the histopathological feature of isolated arrector pili muscles and by the presence of associated extracutaneous features in the form of encephalocraniocutaneous lipomatosis. In particular, nevus psiloliparus can be separated from the Hoffmann-Zurhelle nevus that has so far never been observed in cases of encephalocraniocutaneous lipomatosis. Conclusion: The presently available data suggest that nevus psiloliparus represents a distinct cutaneous entity. Future clinical and genetic research should show whether this concept holds true.