"Pellagra" like skin lesion occurs with:

Carcinoid tumors produce the vasoactive substance, Serotonin.A pellagra-like syndrome is probably caused by diversion of large amounts of tryptophan from the synthesis of Vitamin B3 niacin, which is needed for NAD production, to the synthesis of serotonin and other 5-hydroxyindoles(ref:Harper's 27/e p458)