Epidemiology

Seborrhoeic keratoses are one of the most common skin tumours.[1]​​[7]​​ Men and women are affected equally. The prevalence of seborrhoeic keratosis increases with age and sun exposure.[3]​ 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 seborrhoeic keratosis was 1.4% in people aged between 16-20 years, 24.2% aged between 41-50 years, and 66.7% aged between 61-70 years.[9]​ 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]​ The trunk and forehead are most commonly affected.[11]

There are many different subtypes of seborrhoeic keratosis. Dermatosis papulosa nigra is a common subtype of seborrhoeic 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][12]​​

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