Lactase persistence/non‐persistence genetic variants in irritable bowel syndrome in an endemic area for lactose malabsorption

Background and Aim Lactase non‐persistence is common in I ndia. We evaluated: (i) frequency of lactase gene ( C / T ‐13910 and G / A ‐22018) polymorphisms in irritable bowel syndrome ( IBS ) and healthy controls ( HC ), (ii) association between these polymorphisms and IBS ‐subtypes and symptoms. Methods A total of 150 IBS patients ( R ome‐ III criteria) and 252 age and gender‐matched HC were evaluated for C / T ‐13910 and G / A ‐22018 genotypes using polymerase chain reaction‐restriction fragment length polymorphism ( PCR‐RFLP ). Results Totals of 79 (52%), 52 (35%) and 19 (13%) patients had diarrhea‐predominant IBS ( D ‐ IBS) , constipation predominant IBS ( C ‐ IBS ) and alternating diarrhea and constipation IBS ( A ‐ IBS ), respectively ( R ome‐ III ). Frequency of C / T ‐13910 [genotypes: CC 102 (68%), CT 43 (29%), TT 5 (3%) vs CC 155 (61%), CT 83 (33%), TT 14 (6%), P  > 0.05] and G / A ‐22018 [ GG 97 (65%), GA 41 (27%), AA 12 (8%) vs GG 154 (61%), GA 78 (31%), AA 20 (8%), P  > 0.05] were similar among IBS and HC . Patients with D ‐ IBS more often had C / T ‐13910 and G / A ‐22018 genotypes than C ‐ IBS ( CC 71 [90%], CT 6 [8%], TT 2 [2%]) versus (24 [46%], 25 [48%], 3 [6%]), A ‐ IBS (7 [39%], 12 [63%], 0, [0%]) and HC (155 [61%], 83 [33%], 14 [6%]), P  < 0.0001 and ( GG 69 [87%], GA 6 [8%], AA 4 [5%]) vs (22 [42%], 24 [46%], 6 [12%]) vs (6 [32%], 11 [58%], 2 [10%]), P  < 0.0001. IBS with CC and GG genotypes more often had abdominal pain ( P  = 0.005), distension ( P  = 0.031) and higher stool frequency ( P  = 0.003) and reported symptoms following dairy products than non‐ CC ( P  < 0.0001). Conclusion Though C / T ‐13910 and G / A ‐22018 polymorphisms were comparable among IBS and HC , these were more common among D ‐ IBS and reported some symptoms like abdominal pain, bloating and exacerbation by dairy products.