Integration: Unifying Concept
No matter whether acanthosis nigricans is due to an endocrine disturbance or a visceral neoplasm, its clinical and histopathologic attributes are identical. As noted above, both endocrine- and neoplasia-induced acanthosis nigricans wane when the underlying condition is addressed.
There is a morphologically identical condition to acanthosis nigricans—confluent and reticulated papillomatosis of Gougerot and Carteaud. This condition causes plaques on the anterior trunk, seemingly unrelated to the metabolic disturbances that cause acanthosis nigricans. The larger papules and polypoid excrescences that are seen in acanthosis nigricans do not occur in confluent and reticulated papillomatosis.
While the exact cause of most cases of acanthosis nigricans is not known, some evidence suggests that insulin resistance is a major factor. This may also be true for confluent and reticulated papillomatosis of Gougerot and Carteaud as well. Obesity is the most common cause of insulin resistance and acanthosis nigricans. Insulin resistance can enhance cellular proliferation and inhibit apoptosis, but the exact way in which it leads to over-production of keratin as well is not known. Some familial cases of acanthosis nigricans are due to mutations in fibroblast growth factor receptor 3.