Gene/Protein Disease Symptom Drug Enzyme Compound
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Hereditary hemochromatosis (HH) is a common autosomal recessive disorder that can result in iron overload and a wide range of clinical complications, including hepatic cirrhosis, diabetes mellitus, hypopituitarism, hypogonadism, arthritis, and cardiomyopathy. People with HH can be detected at an asymptomatic stage of the disease by abnormalities in serum iron measures. Early detection is desirable, because periodic phlebotomy provides effective treatment for iron overload and may prevent complications of the disorder. The natural history of HH is poorly understood, however, and the proportion of people detected by screening who will develop serious complications of HH is unknown. The genetics of HH may help to resolve these questions. The gene, HFE, and two mutations, C282Y and H63D, have been identified: the C282Y mutation has a higher penetrance than the H63D mutation, and appears to result in a greater loss of HFE protein function. Most people with HH are C282Y homozygotes, a small proportion are compound heterozygotes or H63D homozygotes, and some have no identifiable HFE mutation or are HFE heterozygotes, suggesting that additional mutations associated with HH are yet to be found. Gender and environmental agents, such as alcohol and dietary iron, influence phenotypic expression of HH. The severity of HH is thus determined by an interaction between genotype and modifying factors. HFE mutations also appear to increase the likelihood of iron overload in inherited anemias and to promote the clinical manifestations of porphyria cutanea tarda. HH is an important paradigm for medical genetics because it offers an opportunity to explore the complexity of gene gene and gene environment interactions.
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PMID:Hemochromatosis: genetics helps to define a multifactorial disease. 972 31

Like most essential nutrients, Fe needs to be maintained in the body at a defined level for optimal health, with appropriate adaptation to varying Fe needs and supply. The primary mechanism for controlling Fe level is the regulation of Fe absorption. Several different proteins have been identified as contributors to the process. Despite a complex regulatory system, Fe disorders (both Fe deficiency and Fe overload) occur. Fe deficiency is a common problem worldwide, resulting from inadequate dietary Fe and blood loss. Complications include pre-term labour, developmental delay, and impaired work efficiency. No specific genetic syndromes causing isolated Fe deficiency have been described, but animal studies and clinical observations suggest that such a relationship may be a possibility. Conversely, the known causes of Fe overload are genetic. Fe overload is less common than Fe deficiency, but can result in serious medical complications, including cirrhosis, primary liver cancer, diabetes, cardiomyopathy and arthritis. The most common and best characterized syndrome of Fe overload is hereditary haemochromatosis (HHC), an autosomal recessive disorder. Mutations in the HFE protein cause HHC, but the clinical presentation is variable. Of particular interest is the factor that some FIFE genotypes appear to be associated with protection from Fe deficiency. Other genetic variants in the regulatory pathway may influence the likelihood of Fe deficiency and Fe overload. Studies of genetic variants in HFE and other regulatory proteins provide important tools for studying the biological processes in Fe regulation. This work is likely to lead to new insights into Fe disorders and potentially to new therapeutic approaches. It will not be complete, however, until coordinated study of both genetic and nutritional factors is undertaken.
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PMID:Iron deficiency and iron overload: effects of diet and genes. 1131 Apr 26

Interpretation of laboratory parameters in cases of haemochromatosis can be difficult. Here, we describe two patients with markedly elevated transferrin saturation and high ferritin levels. The first patient is a 51-year-old woman who had been complaining of fatigue, abdominal pain and arthritis for three years. Her liver enzymes were mildly elevated. Secondary causes of iron overload had been excluded. DNA investigation found a homozygous p.Cys282Tyr mutation in the HFE protein, consistent with hereditary haemochromatosis. The second patient is a 58-year-old man with general malaise and cholestatic liver injury. The p.Cys282Tyr and p.His63Asp mutations in the HFE protein could not be detected. Ultrasound of the liver revealed steatosis. The patient was a heavy drinker and a diagnosis of iron overload caused by alcoholic liver disease was made. Based on these case reports, we discuss the strategy to diagnose haemochromatosis and the background of associated laboratory tests.
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PMID:[Diagnosis of haemochromatosis]. 2914 99