By Michael Linenberger, MD
2008-05-01
Dr. Linenberger indicated no relevant conflicts of interest.
Allen KJ, et al. Iron-overload-related disease in HFE hereditary hemochromatosis. N Engl J Med. 2008;358:221-30.
Waalen J, Felitti VJ, Gelbart T, et al. Screening for hemochromatosis by measuring ferritin levels: a more effective approach. Blood. 2008;111:3373-6.
Since the discovery of the homozygous C282Y mutation of the HFE
gene as the major cause of hereditary iron overload in Caucasians of
Northern European descent, numerous studies have attempted to define
the risk of iron-overload-related disease and a practical rationale for
screening. The interpretation of cross-sectional population and
family-based studies has been controversial,1,2 related to
concerns about ascertainment bias, observer bias, insufficient control
groups, and variable definitions of disease penetrance. Longitudinal
cohort studies have involved relatively few HFE homozygotes
and mostly women, thus raising issues about gender bias and other
confounding variables. The U.S. Preventive Services Task Force
recommendation against genetic screening cited the need for more
information on the clinical penetrance of HFE-associated
disease, factors affecting phenotypic expression, and outcomes from
prospective follow-up and therapeutic intervention trials.3
Allen, et al. analyzed 12-year biochemical and clinical data on
1,438 adults of Northern European ancestry (99 percent 40 to 69 years
old) participating in a longitudinal health study. The 203 C282Y
homozygotes and matched controls with other HFE genotypes or
no mutations underwent baseline and follow-up interviews, blinded
physical exams, and laboratory studies. Liver biopsies were performed
on 16 of 33 men and one of seven women HFE homozygotes who
had at least one serum ferritin >1,000 µg/L. Among those with
documented iron overload, clinical disease occurred in 21 of 74 men
(28.4 percent) and one of 84 women (1.2 percent); including
hepatocellular carcinoma (n=2), liver fibrosis or cirrhosis (n=12),
elevated transaminases (n=6), abnormal metacarpophalangeal joints
(n=5), or other hemochromatosis-related symptoms (n=11). Serum ferritin
≥1,000 µg/L was significantly associated with fatigue, liver disease,
use of arthritis medication at baseline, and elevated transaminases,
but not associated with diabetes or joint arthropathy. One non-C282Y
homozygote had clinical disease. Waalen, et al. observed a serum
ferritin level >1,000 µg/L in 59 of 29,699 white adults (0.2
percent) in the Scripps-Kaiser hemochromatosis study, including 20
C282Y homozygotes and four with other HFE genotypes, only one
of whom had liver cirrhosis. (The number of biopsies was not reported.)
Hyperferritinemia in 30 of the 35 without HFE mutations (86
percent) was attributable to excess alcohol, cancer, liver disorders,
or hemolytic anemia. The researchers concluded that a single serum
ferritin determination could serve as a cost-effective screen for the
most threatening HFE mutation-associated complication (liver cirrhosis). Ferritin was also valuable in identifying non-HFE disorders, similar to observations among multi-ethnic populations.4
The report by Allen, et al. supports prior
observations that iron-overload-related disease, when broadly defined,
affects roughly a quarter of male HFE C282Y homozygotes.1
Both reports confirm data from others that liver cirrhosis develops at
a serum ferritin >1,000 µg/L. Importantly, however, pre-cirrhotic
fibrosis is found in 28 percent of asymptomatic C282Y homozygotes with
a ferritin of 500 to 1,000 µg/L (mostly middle-aged males) and
phlebotomy reverses this process.5 Thus, using a ferritin of
>1,000 µg/L for screening, rather than the conventional thresholds
of >200 µg/L for premenopausal women and >300 µg/L for other
adults, may fail to identify some high-risk homozygotes before
irreversible liver injury develops. Despite new understanding, a
risk-adapted screening and management approach to HFE hemochromatosis still awaits answers to the following questions:
How do genetic, lifestyle, and other co-factors affect progression or "nonexpression" of iron overload and liver disease?
Are other tissues (joint, endocrine, cardiac) at risk? If so, by what mechanisms?
What clinical and/or biochemical parameters (e.g., ferritin level) should be used to initiate therapeutic phlebotomy?
Ajioka RS and Kushner JP. Clinical consequences of iron overload in hemochromatosis homozygotes. Blood. 2003;101:3351-3.
Beutler E. Rebuttal to Ajioka and Kushner. Blood. 2003;101:3354-7.
U.S. Preventive Services Task Force. Screening for hemochromatosis: recommendation statement. Ann Intern Med. 2006;145:204-8.
Adams PC, Reboussin DM, Barton JC, et al. Hemochromatosis and iron-overload screening in a racially diverse population. N Engl J Med. 2005;352:1769-78.
Powell LW, Dixon JL, Ramm GA et al. Screening for hemochromatosis in asymptomatic subjects with or without a family history. Arch Intern Med. 2006;166:294-301.
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