Is it farther or further?
chronic disease caused by dietary deficiency and characterized by skin eruptions, 1811, a hybrid formed from Latin pellis "skin" (see film (n.)) + Greek agra "a catching, seizure," related to agrein "to take, seize." But OED suggests it might be originally Italian pelle agra "rough skin." Related: Pellagrous.
pellagra pel·lag·ra (pə-lāg'rə, -lā'grə, -lä'-)
A disease caused by a deficiency of niacin and protein in the diet and characterized by skin eruptions, digestive and nervous system disturbances, and eventual mental deterioration.