Factors influencing disease expression in hemochromatosis

Genetic hemochromatosis is one of the most common inherited disorders in Caucasian populations. The disease frequency in Caucasian populations in Australia, Europe, and the United States is 1:300-400. The basic genetic defect remains unknown, although the hemochromatosis gene is closely linked to histocompatibility antigen (HLA) A, thus allowing early diagnosis in members of affected families. Many factors-environmental, genetic, and nongenetic in nature-influence the degree of iron loading in affected individuals. In particular, pathologic and physiologic blood loss and blood donation influence iron stores in hemochromatosis. The iron concentration in the liver is an important determinant of survival because a hepatic iron concentration in excess of 400 mumol/g dry weight is usually associated with cirrhosis. Patients with cirrhosis secondary to hemochromatosis are at risk of heptocellular carcinoma and complications of portal hypertension. The combination of improved awareness of the condition and the use of HLA typing to identify affected family members has led to earlier diagnosis and therapy, and to an improvement in overall survival.