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Congenital Erythropoietic Porphyria

Congenital Erythropoietic Porphyria (CEP) is caused by faulty enzyme activity and results in brownish discoloration of the teeth and urine in affected cats.

Key Signs

Brownish teeth, Brownish urine

Age of Onset

0 to 2 yrs

Juvenile onset


Autosomal Recessive

For autosomal recessive disorders, cats with two copies of the variant are at risk of developing the condition. Cats with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their kittens if bred.

Likelihood of the Condition

Moderate-high likelihood

At risk cats are likely to show signs of this disease in their lifetime.

What to Do

Here’s how to care for a cat with CEP

Partner with your veterinarian to make a plan regarding your cat’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.

For Veterinarians

Here’s what a vet needs to know about CEP

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.

For Breeders

Planning to breed a cat with this genetic variant?

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.

Technical Details

Variant G>A
Chromosome D2
Coordinate 83,467,845

All coordinates reference FelCat9.0

References & Credit

Credit to our scientific colleagues:

Clavero, S., Bishop, D. F., Giger, U., Haskins, M. E., & Desnick, R. J. (2010). Feline congenital erythropoietic porphyria: Two homozygous UROS missense mutations cause the enzyme deficiency and porphyrin accumulation. Molecular Medicine, 16(9–10), 381–388. View the article