The aetiology of Type 1 diabetes involves both genetic and environmental fa
ctors. The genes implicated are 'susceptibility genes', which modify risk.
Individual susceptibility genes may not be required and are not sufficient
for disease development. The strongest genetic risk component is encoded wi
thin the major histocompatibility complex (MHC) and is designated IDDM1. Th
e HLA-DQ genes contribute to the risk, but so may other MHC-encoded genes.
The susceptibility encoded by IDDM2 refers to a variable number of tandem r
epeats in the insulin gene region. Many other genomic regions have been des
ignated as susceptibility intervals potentially containing candidate genes.
Environmental factors appear to be important in disease expression in eith
er a causative or a protective role. Epidemiological data indicate that suc
h factors operate from early in life. Viral infection(s) may have a disease
-initiating and/ or accelerating effect. A potential diabetogenic role for
cows' milk protein remains unconfirmed. Further research is necessary to el
ucidate fully the aetiological factors involved and how they interact.