Chapter 69: Hemochromatosis

Hemochromatosis is a heterogeneous group of heritable disorders that increase the risk of developing iron overload due to increased dietary absorption of iron. Most hemochromatosis is due to mutation(s) in genes that alter the expression, structure, or ferroportin binding of hepcidin, a liver polypeptide that is the central regulator of iron absorption. Deleterious mutations that cause hemochromatosis include those of the HFE, HJV, TFR2, HAMP, and SLC40A1 genes. A rare mutation in the iron-responsive element of the FTH1 gene caused hemochromatosis due to decreased ferritin heavy-chain ferroxidase activity. Because mechanisms to excrete iron are limited, some persons with hemochromatosis develop iron overload and consequent target organ injury

Epidemiology

Prevalence

HFE hemochromatosis:

• 4–10 per thousand (western European whites)

• 4–5 per thousand (non-Hispanic whites in United States)

• 1 in 200 (U.S. Vietnamese)

Non-HFE hemochromatosis:

Rare, based on pathogenic mutations and cases discovered in population samples

Race/ethnicity:

HFE hemochromatosis:

Predominantly European whites; some Native Americans, U.S. Vietnamese, Hispanics, African Americans

Non-HFE hemochromatosis:

Predominantly European whites; some Asians, Native Africans, African Americans, Japanese, Pacific Islanders

Male-to-female ratios in HFE hemochromatosis diagnosed in medical care:

• Hemochromatosis genotype: 1:1

• Elevated serum iron measures: 1.3:1

• Elevated hepatic transaminase levels: 2:1

• Diabetes mellitus: 4:1

• Cirrhosis: 5:1

• Primary liver cancer: 5:1

Age:

HFE hemochromatosis:

Severe iron overload typically occurs in subjects 40–60 years old but is rare before age 30 years

Non-HFE hemochromatosis:

Severe iron overload is common in children, adolescents, or young adults with HJV, TFR2, or “gain-of-function” SLC40A1 hemochromatosis

Life expectancy:

Normal in treated patients without cardiomyopathy, cirrhosis, or diabetes mellitus, and in individuals who do not develop iron overload

Mortality rate in U.S. Adults:

• Men: 2.4/million

• Women: 1.2/million

• Whites: 1.9/million

• Nonwhites: 1/million

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Witte DL et al. Clin Chim Acta 1996;245:139–200

Yang Q et al. Ann Intern Med 1998;129:946–953

Etiology and Classification