An evaluation of the MLC1 rs2076127 G/A polymorphism, found a strong association with schizophrenia in the family-based design, but no effect in the unrelated case-control design [17]; the same scenario was seen for the putative association of CRTH2 (G1544C) with asthma [18] and for the putative association of 5q31 C2063G with Crohn disease [19]. Here, PTGDR2 is linked to Crohn disease.