A 13-year-old boy presents with nonpruritic, hyperpigmented warty papules and plaques. They are arranged in a unilateral pattern on the left side of his lower abdomen. He has had them since he was 1 year-old. Previously they were flat and tan, but they have become more extensive, thicker, and darker. They are limited to the left lower abdomen area of his body. The remainder of the physical examination is within normal limits, and medical and family histories are unremarkable.
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Epidermal nevi have an incidence of 1 in 1000 people,1 and age of onset ranges from birth to 14 years. They arise from the pluripotent germ cells in the basal layer of the embryonic epidermis, which give rise to keratinocytes and skin appendages.2 They are noncancerous and clinically present as flat, tan patches of skin that progress to raised, velvety plaques.
Epidermal nevi often follow the lines of Blaschko, which are thought to follow the paths along which cells migrate as the skin develops during fetal development.3 They are most commonly linear and are found on the trunk and limbs, rarely occurring on the scalp and face. At birth and in infancy, they are often flat tan or brown marks, but as the child develops, they tend to become thickened and warty.4 They may also become more widespread.
These nevi are often classified according to the predominant type of skin involved in the epidermis, such as keratinocytes, sebaceous glands, hair follicles, or apocrine glands.2 For example, the epidermis is composed of keratinocytes, and this type of nevus is called keratinocytic or nonorganoid epidermal nevi.4 Nevi with prominent adnexal components include the sebaceous, follicular, and apocrine types, and these are referred to as organoid.5 Most patients have a combination of different types of nevi, such as keratinocytic and sebaceous nevi.
The lesions may present with no other abnormalities, or they can present with coexisting conditions of the brain (eg, seizures, agenesis of the corpus callosum), musculoskeletal system (eg, scoliosis, craniofacial deficits), or eyes (eg, corneal opacity, optic nerve deficits).6 Approximately one-third of individuals may have involvement of another organ system, diagnosed as epidermal nevus syndrome.6 Solomon syndrome involves neurocutaneous involvement of the skin, brain, eyes, and/or skeleton.7 Schimmelpenning syndrome presents with neurologic deficits.7
Epidermal nevi show no inheritance pattern but seem to arise from mutations during embryogenesis. Mutations in the fibroblast growth factor receptor 3 (FGFR3) gene have been found in 30% of people with keratinocytic epidermal nevi;3these mutations are known to cause thanatophoric dysplasia, which may occur with acanthosis nigricans. Acanthosis nigricans and certain epidermal nevi share common clinical and histologic findings.
The use of topical and intralesional steroids, dithranol, topical retinoids, and cryosurgery are usually not effective against epidermal nevi.6 Topical calcipotriol can be effective; however, it is not approved for children under age 12 years in the United States.3 The nevi can be removed by surgery in certain conditions.
Nina Patel, BS, is a student at the University of Texas Medical School at Houston.
Maura Holcomb, MD, is a resident at Baylor College of Medicine in Houston, Texas.
1. Hafner C, van Oers JM, Vogt T, et al. Mosaicism of activating FGFR3 mutations in human skin causes epidermal nevi. J Clin Invest. 2006;116(8):2201-2207.
2. Rogers M, McCrossin I, Commens C. Epidermal nevi and the epidermal nevus syndrome: a review of 131 cases. J Am Acad Dermatol. 1989;20(3):476-488.
3. National Library of Medicine. Genetics Home Reference. Epidermal nevus. http://ghr.nlm.nih.gov/condition/epidermal-nevus. June 2011. Accessed April 7, 2016.
4. Ngan V. DermNet NZ. Epidermal naevi. http://www.dermnetnz.org/lesions/epidermal-naevi.html. Updated January 1, 2016. Accessed April 7, 2016.
5. Happle R. The group of epidermal nevus syndromes. Part I. Well-defined phenotypes. J Am Acad Dermatol.2010;63(1):1-22.
6. Schwartz RA, Jozwiak S. Epidermal Nevus Syndrome. Medscape Drugs & Diseases. http://emedicine.medscape.com/article/1117506-overview. Updated May 28, 2015. Accessed April 7, 2016.