TYPE 1 DIABETES MELLITUS
TIDM is a genetic disease of the immune
system and the genes responsible for this dis
ease are carried on the DQ band (a designa
tion of a specific band in the genetic mark-
ers) of the short arm of the chromosome.
Genes in this area are known as the Major
Histocompatibility System and control the im-
mune system. These are the genes that are
matched for organ transplant. When some
of these genes malfunction or are abnormal,
they can impair the immune system's abil
ity to recognize itself. Autoimmune diseases
such as T1DM and others, eg, rheuma-
toid arthritis
are the result. A few genes
discovered
so far for TIDM are called
HLA-DQA1*0301. HLA-DQA1*0302, HLA-DQ
0602, and HLA-DQW 1.2. Some genes ap
pear to protect against diabetes. Genetics is
not the whole story, however, since not ev-
eryone with these genes develops the disease.
Only about 50% of identical twins get the
disease. There must therefore be some en-
vironmental factors involved that trigger the
immune system to attack the
B cells of
the pancreas and destroy them, causing in-
sulin deficiency and diabetes. The environ
mental factors that trigger the destruction
of B cells are not yet fully identified. tain viruses, such as coxsackie viruses, have
been identified in some patients. Cow's milk
has also been suspected but data so far are
ncomplete. There are probably other enri
ronmental precipitating factors yet to be iden-
tified and studies are going on for this pur.
pose. Many of these studies are being done
in Europe especially in Scandinavia where the
prevalence of
TIDM is the highest
There are at least 3 forms of TIDM, The
commonest form of the disease is that which
occurs most during the preadolescent growth