Seborrheic keratoses are one of the most common skin tumors.[1]Seaton E, Madan V. Benign keratinocytic acanthomas and proliferations. In: Barker J, Griffiths C, Bleiker T, eds. Rook's textbook of dermatology. 10th ed. Hoboken, NJ: John Wiley & Sons, Ltd; 2024.[7]Barthelmann S, Butsch F, Lang BM, et al. Seborrheic keratosis. J Dtsch Dermatol Ges. 2023 Mar;21(3):265-77.
https://onlinelibrary.wiley.com/doi/10.1111/ddg.14984
http://www.ncbi.nlm.nih.gov/pubmed/36892019?tool=bestpractice.com
Men and women are affected equally. The prevalence of seborrheic keratosis increases with age and sun exposure.[3]Yeatman JM, Kilkenny M, Marks R. The prevalence of seborrhoeic keratoses in an Australian population: does exposure to sunlight play a part in their frequency? Br J Dermatol. 1997;137:411-414.
http://www.ncbi.nlm.nih.gov/pubmed/9349339?tool=bestpractice.com
In people with white skin, they are common over the age of 60 years and uncommon under age 30 years. In a survey of workers in Germany, the prevalence of seborrheic keratosis was 1.4% in people ages between 16-20 years, 24.2% ages between 41-50 years, and 66.7% ages between 61-70 years.[9]Augustin M, Herberger K, Hintzen S, et al. Prevalence of skin lesions and need for treatment in a cohort of 90 880 workers. Br J Dermatol. 2011 Oct;165(4):865-73.
https://academic.oup.com/bjd/article-abstract/165/4/865/6643919
http://www.ncbi.nlm.nih.gov/pubmed/21623753?tool=bestpractice.com
In a survey of female volunteers in Indonesia, the prevalence was 47% in the 20-30 year age group and increased to 59% in the 41-50 year age group and 65% in the 51-60 year age group.[10]Du Y, Doraiswamy C, Mao J, et al. Facial skin characteristics and concerns in Indonesia: a cross-sectional observational study. Skin Res Technol. 2022 Sep;28(5):719-28.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9907585
http://www.ncbi.nlm.nih.gov/pubmed/35785442?tool=bestpractice.com
The trunk and forehead are most commonly affected.[11]Jackson JM, Alexis A, Berman B, et al. Current understanding of seborrheic keratosis: prevalence, etiology, clinical presentation, diagnosis, and management. J Drugs Dermatol. 2015 Oct;14(10):1119-25.
http://www.ncbi.nlm.nih.gov/pubmed/26461823?tool=bestpractice.com
There are many different subtypes of seborrheic keratosis. Dermatosis papulosa nigra is a common subtype of seborrheic keratosis which is more prevalent in people with brown and black skin (Fitzpatrick skin type IV, V, or VI). Lesions usually start to appear in adolescence and are usually found on the face, neck, and chest; incidence increases with age.[1]Seaton E, Madan V. Benign keratinocytic acanthomas and proliferations. In: Barker J, Griffiths C, Bleiker T, eds. Rook's textbook of dermatology. 10th ed. Hoboken, NJ: John Wiley & Sons, Ltd; 2024.[12]Bhat RM, Patrao N, Monteiro R, et al. A clinical, dermoscopic, and histopathological study of dermatosis papulosa nigra (DPN) - an Indian perspective. Int J Dermatol. 2017 Sep;56(9):957-60.
http://www.ncbi.nlm.nih.gov/pubmed/28485013?tool=bestpractice.com