PITRM1 and Alzheimer disease: Detailed investigations of molecular QTL regulation at AD risk loci illustrated diverse qQTL patterns, with enrichment at distributional extremes (τ = 0.1 and 0.9) suggesting genetic effects operating under specific biological conditions, and revealed what standard approaches miss: linear regression failed to detect PITRM1, which exhibited symmetric variance effects where certain genotypes show greater phenotypic plasticity without clear directional impact.