For SCZ, the strongest association is in the extended MHC region (chr6:27–33 Mb). The evidence for association is compelling but high gene density and exceptionally high linkage disequilibrium complicate the identification of specific sequence variation. Although tempting to propose that the association supports long-standing hypotheses concerning roles in SCZ for intra-uterine infection, autoimmunity, or even synaptic pruning (in which MHC genes play a role), this lack of precision renders such propositions speculative.
