Porphyria (por-FEAR-e-uh) refers to a group of rare disorders that result from a buildup of natural chemicals called porphyrins in the body. Porphyrins are needed to make heme, a part of hemoglobin. Hemoglobin is a protein in red blood cells. It carries oxygen to the body's organs and tissues.
Cyril acquired the cat from a tenant in a to-be-demolished tenement featured in the Christmas episode preceding Season 13 proper. As most city cats commonly roamed the streets, even the elderly tenant who was feeding it didn't try to take it with her when she was rehoused; instead, she asked Cyril & her neighbors to check on it regularly & feed it sometimes.