Acanthosis nigricans (AN) is a recognizable skin condition characterized by velvety, hyperpigmented, thickened lesions in body folds. It is associated with various diseases, including type 2 diabetes and obesity, where insulin resistance and hyperinsulinemia are common. This case report describes an 11-year-old patient with AN since birth, who has experienced increasing intensity and distribution of hyperpigmentation, becoming diffuse throughout the body and more pronounced in large folds. The skin appears pachydermiform, thicker, velvety, and rough in areas like the neck, armpits, cubital fossa, wrists, groin, buttocks, knees, and ankles, giving it a dirty appearance. The patient also exhibits distinctive facial features, such as a wide nasal bridge, hypertelorism, and large eyes. Eczematous lesions are observed in both nostrils, and the hands have a velvety cobblestone appearance. Radiological findings include fingerprinting of the brain due to craniosynostosis, causing pressure on the inner table of the skull. The patient also shows dental disease, such as dental chaos and crowded teeth. Histopathology is suggested for educational purposes. **Keywords:** acanthosis nigricans; diabetes mellitus; insulin resistance; obesity; acanthosis; polycystic ovary.Acanthosis nigricans (AN) is a recognizable skin condition characterized by velvety, hyperpigmented, thickened lesions in body folds. It is associated with various diseases, including type 2 diabetes and obesity, where insulin resistance and hyperinsulinemia are common. This case report describes an 11-year-old patient with AN since birth, who has experienced increasing intensity and distribution of hyperpigmentation, becoming diffuse throughout the body and more pronounced in large folds. The skin appears pachydermiform, thicker, velvety, and rough in areas like the neck, armpits, cubital fossa, wrists, groin, buttocks, knees, and ankles, giving it a dirty appearance. The patient also exhibits distinctive facial features, such as a wide nasal bridge, hypertelorism, and large eyes. Eczematous lesions are observed in both nostrils, and the hands have a velvety cobblestone appearance. Radiological findings include fingerprinting of the brain due to craniosynostosis, causing pressure on the inner table of the skull. The patient also shows dental disease, such as dental chaos and crowded teeth. Histopathology is suggested for educational purposes. **Keywords:** acanthosis nigricans; diabetes mellitus; insulin resistance; obesity; acanthosis; polycystic ovary.