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Several people have asked about genetic testing for Celiac Disease.  I am not
a medical professional, but I have learned a little about this topic from my
contacts, and from reading the excellent medical textbook 'Coeliac Disease'
edited by Michael Marsh and published in 1992 by Blackwell Scientific (ISBN
0-632-03097-6).  This book covers many Celiac subjects in great deal. Its
main disadvantage is its price (over $200) but some medical libraries carry
it.

My understanding is that about 25% of the population in the US and Western
Europe has the genetic HLA markers which are associated with Celiac Disease.
The current state of the art of genetic testing cannot predict which of those
within the 25% will get CD, so this test is of greatest value to those in the
'other' 75% for which CD can essentially be ruled out.

The HLA markers for CD are the same markers associated with juvenile
diabetes.  My brother has diabetes, and my son has CD, so it was not
surprising when I was tested to find that I am a carrier of this HLA marker.

When one speaks about HLA markers, it is not the same as speaking about
genes.  HLA testing is cruder.  An analogy one doctor gave me was that gene
testing is like looking for a spelling mistake in one word of an
encyclopedia, whereas HLA testing is like finding the page with the spelling
mistake somewhere on it.

HLA terminology is very complex.  To make matters worse, the geneticists have
changed the coding they use.  DR3 is the most common term used to describe
the particular HLA marker most often seen in CD.  That same marker is now
called DRw17.  Either way, this marker is usually seen in concert with other
HLA markers which are together termed an 'extended haplotype'.  Most people
do not have extended haplotypes.  Those that do have a greater tendency to
come down with autoimmune disorders than the rest of the population.  The
B8-SC01-DR3-DQ2 extended haplotype (note the DR3 inside) is the most common
in the US population, and the great majority of Celiacs have at least one or
their two chromosomes with this extended haplotype.

According to Dr. Martin Kagnoff (who wrote the chapter on genetics in the
Marsh book), essentially all Celiacs have two particular _subfactors_ of HLA
markers.  If a person has just one copy of the gene which codes for DR3, they
automatically get both the subfactors and become part of the HLA risk group.
There is another way to get these two subfactors, and that is to have DR5 on
one chromosome and DR7 on the other.  These people are called DR5/7
heterozygotes, but these people are a minority of CD cases.

I had an opportunity to meet Dr. Kagnoff, and asked him what happens if a
person has both chromosomes with DR3 instead of just one.  His reply was that
this has not been completely researched, but it appears that it results in a
somewhat more several case of Celiac.

Kagnoff and others suspect that there are additional genes involved in CD,
and research continues.  It is possible that more predictive markers will be
discovered in the future.  Since HLA typing is expensive ($350 to $550 in Los
Angeles), and not very predictive, it is hard to justify.  If you are part of
a family with two siblings with CD, free HLA typing may be available through
a research project in Utah.  Do a search of the archives on  "Utah and gene'
to find the announcement.

Bill Elkus