A 19-year-old Japanese man with confluent and reticulated papillomatosis (CRP) is presented. He was an obese and dark-complexioned man, who had impaired glucose tolerance and hyperinsulinemia. The clinical and histological findings were consistent with the diagnosis of CRP. He also had acanthosis nigricans (AN) on his axillae and nape. Neither spores nor hyphae were detected from scales; antifungal treatment had no benefit. Although the reduction of his weight was unsuccessful, oral etretinate therapy resulted in considerable improvement of both CRP and AN. We reviewed previous case reports in terms of the relation between CRP and AN. Although the two conditions are usually differentiated because of their distinctive clinical features, a close relationship was noted between CRP and AN.