Porphyria is a disease that occurs very rarely in cats where their bodies do not make a specific enzyme that’s used in making red blood cells properly. That enzyme, hydroxymethylbilane synthase (HMBS), sometimes has mutations that affect a cat’s ability to make blood, or cats may not make enough of it.
There are two different kinds of porphyria that affect cats: acute intermittent porphyria (AIP) and congenital erythropoeitic porphyria (CEP).
The most obvious symptoms of porphyria in cats are discolored, reddish brown teeth (erythrodontia), and reddish brown urine. Normally when a cat has reddish brown urine it will be full of red blood cells. With porphyria there will not be any blood in the urine.
Disease Information Sites
There are several research papers discussing porphyria in cats, but no websites devoted to this disease in cats. There are a couple of websites devoted to this disease in humans, but they appear to be of little value for help in understanding this disease in cats.
I couldn’t find a support group specific to porphyria, probably because it’s so rare.
There is a Facebook group for Cats With Multiple Medical Conditions that has members experienced in managing a lot of different diseases or disease combinations. This group may be a good one to join if your cat has, or is suspected to have porphyria.