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Metabolic Liver
Diseases |
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Haemochromatosis is caused by excessive
deposition of iron in tissues.
In haemochromatosis, excessive iron accumulation causes chronic damage to liver
cells. Two types
of disease are distinguished.
Primary haemochromatosis is inherited as an autosomal recessive trait, and leads
to excessive
absorption of iron from the gut.
The gene is located on chromosome 6, in association with the HLA locus.
Iron accumulates as haemosiderin in many tissues including the liver, pancreas,
pituitary, heart and skin. Accumulation of iron in the liver causes death of
hepatocytes (possibly from
the generation of free radicals) and leads to cirrhosis.
Accumulation in the pancreatic islets causes diabetes mellitus, and in the
cardiac muscle gives
rise to a cardio-myopathy with heart failure.
Iron accumulates as haemosiderin in many tissues including the liver, pancreas,
pituitary, heart and skin.
Macroscopically, the liver and other affected tissues appear rusty brown due to
haemosiderin in cells
(hepatocytes, Kupffer cells, and biliary epithelium in the liver).
Diagnosis can be made on the finding of an extremely high saturation of
transferrin in the blood, with
high serum iron and ferritin levels, and is usually confirmed by liver biopsy.
Secondary haemochromatosis (also called haemosiderosis) is the result of
excessive iron
accumulation caused by other primary diseases (e.g. alcoholism) and by repeated
blood transfusions
for diseases with abnormalities of red cell formation, particularly thalassaemia.
Perls' stain reveals iron deposition in tissues as a blue colour. In (a) iron is
seen in liver cells,
as well as in biliary epithelium. Macroscopically, affected tissues look rusty
brown, as illustrated by
the pancreas in (b) taken from a patient with primary haemochromatosis.
Copper accumulation in
alpha1-antitrypsin deficiency causes chronic liver disease and cirrhosis
alpha1-antitrypsin deficiency is an important heritable cause of chronic liver
disease,
and also causes panacinar emphysema.
Affected individuals fail to produce the normal active extracellular protease
inhibitor alpha1-antitrypsin.
Wilson's disease is an inherited disease of copper metabolism
Wilson's disease is a rare but treatable cause of chronic destructive liver
disease.
An inherited autosomal recessive disorder of copper metabolism, it causes excess
copper to
accumulate in the liver and brain. This defect is a mutation in a
copper-transport ATPase gene.
Many alleles for this protease inhibitor gene are known, each of which has been
given a letter.
The normal phenotype is known as PiMM. The most significant abnormal allele is
termed Z.
Heterozygotes (PiZM) carry an increased risk of lung damage if they smoke,
developing emphysema.
Homozygotes (PiZZ) develop emphysema and liver disease.
Disease may be manifest in neonates as a neonatal hepatitis, although this is
not
an inevitable consequence of the PiZZ genotype.
In adult life, disease may be discovered following investigation of abnormal
liver function tests.
Investigation may reveal either a chronic hepatitisor cirrhosis.
Excess copper in the liver initially causes a chronic hepatitis picture
clinically, and
pathologically progresses to cirrhosis. Accumulation in the brain leads to
psychiatric disorders,
abnor-mal eye movements, and movement disorders resembling Parkinson's disease.
Diagnosis can be made by finding a low level of cerulo-plasmin, the
copper-binding protein,
in the serum (as it is not released from the liver).
Excess copper is demonstrable in liver biopsy material by special staining.
Liver biopsy shows accumulation of a1-antitrypsin in hepatocytes as globules
which stain with PAS
(a) and can also be specifically stained by immunoperoxidase methods using
antibodies
to alpha1-antitrypsin (b). |
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