PTGDR encodes the prostaglandin D2 (PGD2) receptor, a G protein-coupled receptor primarily mediating its effects through Gs-protein activation of adenylate cyclase and elevation of intracellular cAMP 1. The receptor also mobilizes calcium and is involved in mast cell maturation and degranulation through PLA2G3-dependent signaling [UniProt]. PTGDR plays a significant role in inflammatory and allergic responses, with multiple promoter polymorphisms influencing gene expression and disease susceptibility. Genetic studies demonstrate population-specific associations with asthma. The -549 C/T polymorphism shows association with asthma in Europeans and adults (OR=1.248, P=0.003), but not in children or Chinese populations 234. Functional analyses reveal that promoter variants alter transcription factor binding patterns and PTGDR expression levels 56. Notably, PTGDR expression is significantly elevated in allergic patients compared to controls (81.4% sensitivity as a biomarker) 7, and retinoic acid receptors upregulate PTGDR expression through response elements, particularly affecting Th2 cytokine responses 8. Glucocorticoid response varies by promoter haplotype, with clinical implications for corticosteroid therapy efficacy 6.