Poliosis overlying a nevus with blue nevus features
1. David Geffen School of Medicine at the University of California, Los Angeles, Dermatology Division. firstname.lastname@example.org
Poliosis is a localized patch of gray or white hair. Because it can be seen with a variety of disorders and drugs, a full history and exam is indicated. Additionally, it can be associated with underlying benign and malignant tumors, necessitating histological identification. We review the lesions that are reported with poliosis. In addition, we will report a case of poliosis overlying an intradermal nevus with congenital as well as blue nevus features. To the best of our knowledge, blue nevus features associated with poliosis have not been previously described.
A 15-year-old girl presented with a congenital lesion on her scalp that was noted to be enlarging over the previous 2 months. Physical exam revealed a 6cm by 3cm soft, well demarcated and violaceous nodule on the right vertex of scalp. Surmounting the nodule were poorly demarcated gray hairs (Fig. 1). The remainder of the exam was normal.
The history of a recently enlarging congenital lesion prompted concern for a possible malignant transformation. Was this a congenital nevus transforming into a melanoma or a plexiform neurofibroma into a neurofibrosarcoma?
Prior to biopsy, a computerized axial tomography scan was performed to determine the size and extent of the nodule. A soft-tissue nodularity without evidence of osseous destruction was noted. Incisional and excisional biopsies revealed an intradermal melanocytic nevus with congenital as well as blue nevus features (Figs. 2 and 3). Histological specimens showed nests of heavily pigmented melanocytes in the upper reticular dermis. Heavily pigmented melanocytes with dendritic processes and pale-staining epithelioid melanocytes were present throughout the reticular dermis between collagen bundles and surrounding adnexal structures. Melanocytes with dendritic processes were highlighted with immunohistochemical staining with antibodies to S100 protein (Fig.4).
The literature regarding poliosis of the scalp has been dominated by case reports. Poliosis has been associated with a variety of diseases, drugs, and lesions. These include Marfan syndrome , Vogt-Koyanagi-Harada disease , sarcoidosis , herpes zoster , and alopecia areata . Drugs, including chloroquine, cyclosporine, and topical prostaglandin F2α analogs  have also been reported to cause poliosis. In addition, poliosis can overlie lesions, including neurofibroma [7, 8, 9], giant congenital nevus , congenital intradermal nevus , nevus depigmentosus , halo nevus , nevus , and melanoma [15, 16].
Why this occurs is curious. Is it caused by destruction or dysfunction of melanocytes? Autoimmune and inflammatory diseases can damage melanocytes, and may explain why poliosis is associated with diseases such as alopecia areata, and herpes zoster, respectively. But what about poliosis associated with drugs? What about it overlying melanocytic lesions? Are melanocytes displaced? Do nevus cells take up melanin? If so, then what is the explanation for poliosis when it is associated with nonmelanocytic lesions such as neurofibromas? The pathogenesis is not known and is likely multifactorial.
Our patient presented at age 15 with an enlarging congenital lesion associated with a gray streak of hair. Previously reported scalp nodules associated with poliosis include both congenital and noncongenital nevi, halo nevi, melanoma, and neurofibroma. There are no prior reports, to the best of our knowledge, of poliosis overlying a nevus with blue nevus features.
Acknowledgement: We would like to acknowledge Scott McClennen, M.D., for taking the photo of the histology slide (Fig. 2).
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