What do identical twin studies reveal about the necessity of environmental factors in autoimmune disease development?

Answer

They strongly suggest that non-genetic, or environmental, factors are necessary to switch the disease process on.

Since identical twins, sharing the same genetics, do not always both develop the disease (concordance rate is often 25%-50%), it implies that external, non-genetic triggers are required for the disease to manifest.

What do identical twin studies reveal about the necessity of environmental factors in autoimmune disease development?
Geneticsdiseasecauseimmune systemautoimmunity