The Hfe gene was identified in 1996 as being the major gene for Haemochromatosis (HH). It is a recessive, inherited disorder; therefore the risk of loading iron will only develop if each copy of the mutation (one from each parent) is defective. Those who inherit the mutation from both parents are homozygous and are likely to develop the disease, whereas those who inherit from one parent are carriers who may show a lesser increase in iron absorption. Three mutations (C282Y; S65C and H63D) account for more than 80% of cases. The discovery of new genes related to HH continues, particularly relating to Juvenile Haemochromatosis.
If one receives the defective gene from only one parent, the person is a carrier (and as such is called ‘heterozygous’) and will not (necessarily) develop ‘full-blown’ iron overload, though he/she may develop slight symptoms Carriers will pass the gene on to their children. The offspring of two carriers will have a 25% (1 in 4) chance of being homozygous.
As there are a number of mutations on the Hfe gene other than C282Y, it is possible that a carrier can carry two different defects and as such be a ‘compound heterozygote’, also at risk of loading iron.
In South Africa 1 in 6 Caucasians are carriers of HH.
A person with HH will either be homozygous for the C282Y mutation, or may be a compound heterozygote. This person’s parents may have: a) both been carriers one had HH and one was a carrier, c) both parents had HH (rare) . Where both parents are carriers it is possible that all children will be affected; all will be carriers or all can be normal.
Grades of Haemochromatosis
EFAPH (The European Federation of Associations for Patients with Haemochromatosis), has compiled a useful chart categorising Haemochromatosis into four grades of Haemochromatosis – from Grade 0 (no clinical signs of the condition) to Grade 4 (organ damage and complications has been detected).
This chart can be found on their website at: http://www.europeanhaemochromatosis.eu/Report2006.pdf
The American Hemochromatosis Society AHS has launched a web site for this rare newborn iron disease. Learn more about NH in newborns and the exciting new treatment which offers new hope for pregnant women who have already had an NH baby.
Visit the AHS web site for Neonatal Hemochromatosis (NH) at http://www.neonatalhemochromatosis.org