Congenital Porphyria in Pigs

A Hepatogenous Photosensitivity Disease of Cattle: I. Experimental Production and Clinical Aspects of the Disease

A hepatogenous photosensitivity disease of cattle caused by feeding of flood damaged alfalfa hay was investigated under experimental conditions. The clinical aspects of the hay-induced disease were characterized and compared with the photosensitization caused by surgically-induced biliary obstruction.

The majority of animals which were fed the hay and all those with ligated bile ducts developed photosensitivity which was regularly accompanied by icterus. Lesions of photosensitization were quite variable in degree of severity among individual animals but were essentially identical in both the hay-induced and surgically-induced disease. In all except the severely affected animals skin lesions were confined to those areas not protected by pigment or dense hair coat. Mild lesions developed in some heavily pigmented areas of severely affected animals where the hair was especially short or thin.

The climatic conditions under which the alfalfa hay developed toxicity and the similarity of the disease syndrome to that of “facial eczema” in New Zealand suggest that the two diseases may be caused by a hepatotoxin of similar nature and origin.

Feline acute intermittent porphyria: a phenocopy masquerading as an erythropoietic porphyria due to dominant and recessive hydroxymethylbilane synthase mutations

Human acute intermittent porphyria (AIP), the most common acute hepatic porphyria, is an autosomal dominant inborn error of heme biosynthesis due to the half-normal activity of hydroxymethylbilane synthase (HMB-synthase). Here, we describe the first naturally occurring animal model of AIP in four unrelated cat lines who presented phenotypically as congenital erythropoietic porphyria (CEP). Affected cats had erythrodontia, brownish urine, fluorescent bones, and markedly elevated urinary uroporphyrin (URO) and coproporphyrin (COPRO) consistent with CEP. However, their uroporphyrinogen-III-synthase (URO-synthase) activities (deficient in CEP) were normal. Notably, affected cats had half-normal HMB-synthase activities and elevated urinary 5-aminolevulinic acid (ALA) and porphobilinogen (PBG), the deficient enzyme and accumulated metabolites in human AIP. Sequencing the feline HMB-synthase gene revealed different mutations in each line: a duplication (c.189dupT), an in-frame 3 bp deletion (c.842_844delGAG) identical to that causing human AIP and two missense mutations, c.250G>A (p.A84T) and c.445C>T (p.R149W). Prokaryotic expression of mutations c.842_844delGAG and c.445C>T resulted in mutant enzymes with <1% wild-type activity, whereas c.250G>A expressed a stable enzyme with approximately 35% of wild-type activity. The discolored teeth from the affected cats contained markedly elevated URO I and III, accounting for the CEP-like phenocopy. In three lines, the phenotype was an autosomal dominant trait, while affected cats with the c.250G>A (p.A84T) mutation were homozygous, a unique recessive form of AIP. These animal models may permit further investigation of the pathogenesis of the acute, life-threatening neurological attacks in human AIP and the evaluation of therapeutic strategies. GenBank Accession Numbers: GQ850461-GQ850464.

Accumulation of protoporphyrin isomers I and III, and multiple decarboxylation products of uroporphyrin in a case of porphyria in a slaughtered pig

Pathological and biochemical examinations were made on tissues from a case of porphyria in a slaughtered pig. Bones, kidneys, teeth and lymph nodes showed a mahogany discoloration. Histologically, the pigment was negative on staining for iron (Gomori) and showed a strong red-orange fluorescence under UV light proving it to be porphyrin. Biochemical studies on the kidney, lymph nodes, bone and bone marrow revealed a 'mixed' erythropoietic protoporphyria-coproporphyria. This indicates that the case presented probably represented both a uroporphyrinogen decarboxylase and uroporphyrinogen-III-cosynthase dysfunction.