Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

IV. Porphyrias
253
FIGURE 8-6 Metabolic basis of bovine congenital
erythropoietic porphyria. The fundamental defect is a deficiency
of UROgenIII-Cosyn leading to the accumulation
of type I uroporphyrins and coproporphyrins. These type
I porphyrins account for the clinical, hematological, and
biochemical features of this disease.
recognized in humans ( Harber et al. , 1964 ; Redeker et al .,
1963). It is inherited as a dominant autosomal trait
( Romeo, 1977 ). Patients do not have the major signs of
CEP such as anemia, porphyrinuria, or discolored teeth.
Photosensitivity of the skin is the only significant clinical
manifestation of the disease, and this is associated with
a high plasma protoporphyrin concentration. In the laboratory,
the most striking findings are the high concentrations
of PROTO IX in the erythrocytes and feces.
In cattle, EPP is inherited as an autosomal recessive
trait in contrast to humans and may be sex linked because
to date it has only been seen in females. The photosensitivity
also seems to diminish in adult life. Affected cattle also
do not have anemia, porphyrinuria, or discoloration of the
teeth. Erythrocyte and fecal protoporphyrins are very high
in comparison to normal cows ( Ruth et al. , 1977 ).
The fundamental enzymatic defect in bovine EPP is a
deficiency of ferrochelatase (FER-Ch) ( Ruth et al. , 1977 ),
which results in the accumulation of PROTO IX. Low
FER-Ch was found in all tissues of EPP calves so that the
defect is a total body defect.
3 . Porphyria of Swine
Porphyria in swine was first recognized in New Zealand
by Clare and Stephens (1944) and later in Denmark
( Jorgensen and With, 1955 ). Porphyria in swine is inherited
as a simple autosomal dominant trait. Except for the
very severe cases, there appears to be little or no effect on
the general health of the pig. Photosensitivity is not seen
even in the white pigs. The predominant feature in the
affected pig is a characteristic reddish discoloration of the
teeth, which fluoresces on exposure to ultraviolet light.
Porphyrin deposition in the teeth of the newborn pig is virtually
pathognomonic of porphyria in swine. Occasionally,
darkly discolored teeth may not fluoresce, but porphyrins
may be extracted from these teeth with 0.5 N HCl ( With,
1955 ). Similar, though less apparent, deposition occurs in
the bones. The porphyrins are principally URO I and have
been found in concentrations of up to 200 μ g/g of teeth or
bones. The liver, spleen, lungs, kidneys, bones, and teeth
are also discolored by another dark pigment, the nature of
which is unknown .
The urine of the affected pig is discolored only in the
more severely affected pig. The 24-h urinary excretion of
uroporphyrins ranged between 100 and 10,000 μ g and for
coproporphyrin, only 50 μ g. These were both the type I
isomers. PBG is absent in the urine. Close similarities in this
pattern of porphyrin excretion to that found in bovine CEP
are apparent, but the localization of the defect in the erythropoietic
tissue has not been established. This disease has
not been observed in pigs since the original occurrences.