--- license: permission_granted topic_id: companion_breed_health_siamese_omia2942_cat category: companion-breed-health title: "Siamese — Porphyria, acute intermittent (hereditary; OMIA-verified breed predisposition)" lang: en source: "OMIA (Online Mendelian Inheritance in Animals, University of Sydney) breed-specific hereditary-disorder record, saved verbatim to source_file; C1 substring-verified. Pulled 2026-08-02 from local OMIA database dump." source_file: pdf-raw/breed-health/siamese_omia2942_2942.txt date_parsed: 2026-08-02 tokens_estimated: 584 verification: method: substring_match claims: 9 passed: 9 date: 2026-08-02 recovered: false path: companion-breed-health/companion_breed_health_siamese_omia2942_cat/01_companion_breed_health_siamese_omia2942_cat.md source_document: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" citation: authority: "OMIA — Online Mendelian Inheritance in Animals (University of Sydney)" title: "Siamese — Porphyria, acute intermittent (hereditary; OMIA-verified breed predisposition)" url: "https://omia.org/OMIA001493/9685/" retrieved: "2026-08-02" ref: "OMIA breed-specific hereditary-disorder records (omia.org), derived from local OMIA database dump; dataset: https://doi.org/10.25910/2AMR-PV70" doc_type: "academic animal-genetics database (breed-specific disorder entries)" needs_review: false
Siamese — Porphyria, acute intermittent (hereditary; OMIA-verified breed predisposition)
Source: first-hand OMIA (University of Sydney) breed-specific hereditary-disorder record, saved verbatim to source_file; every claim below is a C1 byte-substring of it.
Claims
Breed: Siamese (Cat)Disorder:Mode of inheritance: Autosomal dominantSummary: Acute intermittent porphyria (AIP) is a disorder of heme synthesis characterized by erythrodontia (brown discolored teeth) that fluoresce pink under UV light and reddish-brown urine. The presenting signs are very similar to those of congenital erythropoietic porphyria (CEP, OMIA 001175-9685). Cats with AIP have half normal hydroxymethylbilane (HMB) synthase activity, a necessary enzyme in the heme synthesis pathway. Testing of cats that present with AIP-like signs is recommended, since these cats may have either AIP or CEP. Breeding of cats with either condition is discouraged. Edited by Dr. Mark HaskinsClin feat: Signs include erythrodontia (brownish-discolored teeth), brownish urine and bones, with the teeth and bones fluorescent with UV light. Some affected cats have low levels of hemoglobin and iron, decreased hematocrit and mean corpuscular volume, and increased reticulocyte counts. Affected cats have half-normal activity of hydroxymethylbilane (HMB) synthase, and normal uroporphyrinogen III synthase (UROS) activity. Urinary aminolevulinic acid (ALA), porphobilinogen (PBG), uroporphyrin, and coproporphyrin levels are all elevated (Clavero et al., 2010). Cats presenting with brown discolored teeth may have either AIP or CEP. There has so far been one genetically confirmed feline case of CEP (see OMIA 001175-9685), so cats showing these signs are more likely to have AIP.Defect: yesPathology: Affected cats have decreased levels of HMB-synthase, which disrupts the normal heme synthesis pathway. This leads to an accumulation of porphyrins (URO I and COPRO I) in teeth and bones, causing discoloration. The porphyrins are also excreted in urine, causing the brownish tint (Clavero et al., 2010).Control: Testing of cats that present with AIP-like signs is recommended. Breeding of cats with this condition is discouraged.Gen test: Cats presenting with brown discolored teeth and brown urine should be tested for the causative mutations in the HMBS gene. These cats should also be tested for two mutations in the UROS gene that can cause CEP (see OMIA 001175-9685), a similar condition that is caused by a mutation in a different gene.
Associated gene(s)
Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.
- Gene: Entrez Gene ID 4206774 (no symbol in OMIA GeneSynonym) — OMIA Phene_Gene
- OMIA molecular-genetics note: By sequencing the two obvious comparative candidate genes (UROS and HMBS) in affected cats from four unrelated populations, Clavero et al. (2010) identified four different causative mutations in HMBS (one in each population): 1. a 3 bp deletion in exon 14 (c.842_844delGAG, omia.variant:501) 2. a T duplication in exon 5 causing a frameshift and protein truncation (c.189dupT, omia.variant:596) 3. a …
Evidence (references)
Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.
- 1975. Feline congenital erythropoietic porphyria associated with severe anemia and renal disease: clinical, morphologic, and biochemical studies. American Journal of Pathology — PubMed:PMID1231563 — OMIA Phene_Article / Article
- 2010. Feline acute intermittent porphyria: a phenocopy masquerading as an erythropoietic porphyria due to dominant and recessive hydroxymethylbilane synthase mutations. Hum Mol Genet — PubMed:PMID19934113 | DOI:10.1093/hmg/ddp525 — OMIA Phene_Article / Article
- 2013. Diagnosis of feline acute intermittent porphyria presenting with erythrodontia requires molecular analyses. Vet J — PubMed:PMID24239138 | DOI:10.1016/j.tvjl.2013.10.008 — OMIA Phene_Article / Article
- 2025. Animal models of porphyria with hepatic involvement. Semin Liver Dis — PubMed:PMID40840519 | DOI:10.1055/a-2677-6806 — OMIA Phene_Article / Article
Comparative medicine (human OMIM)
Derived from OMIA database dump (omia.xml, local); structured field, not verbatim prose. First-hand values below are verbatim substrings of the topic's pdf-raw/omia/<phene_id>.txt source file.
- OMIM:176000 (type: trait) — OMIA Group_OMIM (via OMIA_ID)
- OMIM:609806 (type: gene) — OMIA Group_OMIM (via OMIA_ID)
verification_derived: method: derived_from_dataset source: "OMIA database dump (omia.xml, local); fields Gene/Variant/Article/OMIM" note: "Structured fields (gene, variant rsID/protein change, PubMed/DOI references, OMIM cross-link) extracted from OMIA dump and presented with first-hand values; not verbatim prose."