RESUMO
Acanthosis nigricans is a skin disorder characterized clinically by abnormally increased coloration [hyperpigmentation] and velvety thickening [hyperkeratosis] of the skin, particularly of skin fold regions, such as of the neck, groin and under the arms [axillae]. Various benign forms have been identified in which may be inherited as primary condition or associated with various underlying syndromes, obesity, use of certain drugs or in association with underlying malignancies. A17-year- old, over weight Libyan male patient presented with two years history of non- itchy dark brown patch over the anterior abdominal wall [above the umbilicus] in a band like configuration, with changes in the skin texture [thickness] and increased skin marking over the lesion. There were no skin tags, no palmoplantar hyperkeratosis. His routine investigations were normal including fasting blood sugar and thyroid function test. Histologically revealed hyperkeratosis, dermal papillimatosis irregular acanthosis and horn pseudocyst. In conclusion, clinically and histologically, our case is consistent with the diagnosis of acanthosis nigricans, with unusual site presentation involving the anterior abdominal wall, which is to the best of our knowledge, has not been reported in the literature