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Feline Acute Intermittent Porphyria (AIP)
| Acronym: | AIP |
| Gene: | HMBS |
| Mutation: | c.189dup, c.250G>A, c.842_844del, c.826-1G>A, c.445C>T, c.107_110del |
| Inheritance: | Autosomal recessive |
| Sample type: | CHS (Cheek Swab), WBE (Whole Blood EDTA) |
Genetics and characteristics
Acute Intermittent Porphyria (AIP) is a group of genetic inborn errors of metabolism resulting from deficient activities of specific enzymes in the heme biosynthetic pathway. Heme is a precursor to hemoglobin and other similar proteins containing iron, which are necessary to bind oxygen in the bloodstream and are usually synthesized in the bone marrow and the liver. Cases of AIP detected in cats are all consequence of different mutations in the HMBS gene encoding for hydroxymethylbilane synthase, an enzyme important in the heme synthesis pathway. Affected cats usually show signs such as brownish urine, fluorescent bones, and markedly elevated urinary uroporphyrin (URO) and coproporphyrin (COPRO). Few cases of AIP have been discovered in Domestic Short Hair and Siamese cats that differ in the specific mutation that occurred in the HMBS gene and the mode of inheritance the diease shows.
Most of the porphyrias in cats show an autosomal dominant mode of inheritance meaning cats that carry one or two mutated HMSB genes will develop the disease. However, few variants of AIP show an autosomal recessive mode of inheritance. That means only cats carrying both mutated genes will develop the disease, whereas cats that carry only one will act as carriers that may potentially pass the mutation to their offspring. Early detection by genetic testing can help identify cats that are affected or carry the specific mutation and help breeders in selecting future mating pairs.
Results Reported As
Test Result |
Interpretation of test result |
CLEAR |
Tested mutation was not detected in animal with „clear“ result. Animal tested as clear has wild-type allele in homozygous state (i.e. two pairs of healthy alleles). It will not develop disease caused by tested mutation.* It will pass only wild-type allele to its offspring. |
CARRIER |
Tested mutation was detected in animal with „carrier“ result. Animal tested as carrier has one wild-type and one mutation allele, it is in heterozygous state. It will not develop disease caused by tested mutation.* It can pass wild-type or mutation allele to its offspring. |
AFFECTED |
Tested mutation was detected in animal with „affected“ result. Animal tested as affected has two copies of mutation alleles affecting the gene. It is likely the animal will experience a genetic disorder due to this mutation.** It will pass only mutation allele to its offspring. |
*Test excludes only tested mutation but not possible unknown mutations or factors that can lead to similar condition/symptoms.
** Potential unknown mutations or multiple other factors can possibly affect the likelihood of experiencing a genetic disorder.
References:
Clavero, S., Ahuja, Y., Bishop, D. F., Kwait, B., Haskins, M. E., Giger, U., Desnick, R. J. (2013). Diagnosis of feline acute intermittent porphyria presenting with erythrodontia requires molecular analyses. Veterinary journal (London, England : 1997), 198(3), 720–722. https://doi.org/10.1016/j.tvjl.2013.10.008
Clavero, S., Bishop, D. F., Haskins, M. E., Giger, U., Kauppinen, R., Desnick, R. J. (2010). Feline acute intermittent porphyria: a phenocopy masquerading as an erythropoietic porphyria due to dominant and recessive hydroxymethylbilane synthase mutations. Human molecular genetics, 19(4), 584–596. https://doi.org/10.1093/hmg/ddp525