Congenital Erythropoietic Porphyria (CEP) is a hereditary disorder caused by the decreased activity of a specific enzyme in the biosynthetic pathway of heme. Affected cats have decreased activity of the uroporphyrinogen-III-synthase enzyme which leads to accumulation of its substrates in various tissues, such as bone and teeth. Similar to Acute Intermittent Porphyria (AIP), the disorder is characterized by the brownish discoloration of the teeth and brownish urine. Bloodwork may show polychromasia. Fluorescence of teeth is a specific diagnostic feature seen in affected cats.

As there is no cure for this disease, therapy is limited to supportive care dictated by the severity of the clinical signs. Although described in other species, a propensity towards photosensitivity remains questionable in cats with this disorder. Owners may consider limiting exposure to sunlight in affected individuals.

There are many responsibilities to consider when breeding cats. Regardless of test results it is important that your cat is in good general health and that you are in a position to care for the kittens if new responsible owners are not found. For first time or novice breeders, advice can be found at most cat registry websites.

This disease is autosomal recessive meaning that two copies of the mutation are needed for disease signs to be shown. A carrier cat with one copy of the CEP mutation can be safely bred with a clear cat with no copies of the CEP mutation. About half of the kittens will have one copy (carriers) and half will have no copies of the CEP mutation. Kittens in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected kittens. Please note: It is possible that disease signs similar to the ones caused by the CEP mutation could develop due to a different genetic or clinical cause.