Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023890 (cirrhosis)
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Four types of hereditary haemochromatosis have been identified. Type 1 is due to a point mutation in the HFE gene (C282Y) and leads via an increase in intestinal iron absorption to iron overload and organ damage. Type 2 is a juvenile form with manifestation before age 30; it affects both gender and is associated with severe cardiomyopathy and hypogonadism. The genetic defect of type 3 is located on chromosome 7q22 and affects the transferrin receptor 2. The consequences of type 3 are similar to those of type 1. The autosomal-dominant type 4 is located on chromosome 2q32 and affects the basolateral iron carrier ferroportin 1. In contrast to types 1 and 3 iron deposits in type 4 are seen predominantly in macrophages; in type 4 serum ferritin is significantly increased although transferrin saturation is only slightly abnormal. The prognosis of haemochromatosis is normal when phlebotomy therapy is started prior to manifestation of cirrhosis or diabetes. Screening strategies should be implemented to improve early detection.
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PMID:[Hereditary hemochromatosis]. 1267 39

Genetic hemochromatosis is classified into four subtypes of which only type 1 is of clinical importance in Caucasians. Type 1 is due to an autosomal recessive inborn error of metabolism; the homozygous C282Y mutation of the HFE gene on chromosome 6 accounts for more than 90% of the clinical phenotype in populations of Celtic origin. The mutation leads to an inadequately high intestinal iron absorption which may finally cause iron overload in and damage to various organs. Type 2 is the juvenile form of iron overload which leads to a severe phenotype prior to age 30 with cardiomyopathy and hypogonadism. The corresponding mutations are located in the hemojuveline and hepcidin genes. Typ 3 has mainly been described in Italian families and refers to mutations in transferrin receptor 2 gene. Histopathologic and clinical consequences of type 3 hemochromatosis are similar to those seen in type 1. Types 2 and 3 are autosomal recessive traits. Type 4 hemochromatosis follows an autosomal dominant trait; the corresponding mutation affects the basolateral iron carrier ferroportin 1. Diagnosis of hemochromatosis is based on determinations of serum ferritin and transferrin saturation with the latter being more sensitive and specific. In case of a homozygous C282Y gene test, liver biopsy is not required for diagnosis. Liver biopsy is, however, recommended in C282Y homozygotes at ferritin values > 1,000 ng/ml because of an increased risk for liver fibrosis. Phlebotomy treatment is the standard care to remove iron in genetic hemochromatosis. Patients treated in the early noncirrhotic stage have a normal life expectancy. Thus, future efforts should aim at early diagnosis. Iron removal also improves the outcome in cirrhotic patients. Liver carcinoma may develop in cirrhotic patients despite iron depletion. Liver cancers without cirrhosis are so rare that screening is only recommended in cirrhotic patients.
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PMID:[Hereditary hemochromatosis]. 2003 60