Genetic background of lactose intolerance and implications for diagnosis

Abstract

with both CC and LC, and if there was associated entempathy. Methods: 32 patients with microscopic colitis (17 CC, 15 LC) diagnosed using objective histological criteria were included. Serum IgA-antiendomysial (AEA) and lgA-human tissue antitransglutaminase (AtTG) antibodies (IIF and ELISA assays, respectively) were investigated, after ruling-out lgA deficiency. The DQ2 hapforype (DQAI*0501 + DQBI*0201) was deterrmned by PCRSSP. This method detects the presence or absence of at least one copy of the haplotype. HLA-DQ2 was also assayed in 50 healthy controls from the general population. Endoscopic biopsies from 2d-3rd portions of duodenum were obtained in DQ2 + patients. The number of intraepithefial lymphocytes (IEL) (N<8 x 20 epithelial cells), their distribution pattern, and the architecture of villi were assessed. Results: 13 of 32 (40.6%) patients with microscopic colitis and 9 of 50 (18%) controls had DQ2 + (p = 0.025). There were no differences between CC and LC (35.3 vs 47%). A LC patient had positive AEA and AtTG, and biopsy with IEL increase (11x20 epithelial cells) without atrophy (Marsh 1); she was diagnosed of CS and a gluten-free diet was started. In the other 30 patients, AEMAtTG were negative. In 7 DQ2 + patients the number of [EL was normal and there was no villous atrophy (in 5 patients endoscopic biopsies were not available). Conclusions: in the present series, the frequency of CS in microscopic colitis patients was 3.2%, lower than that previously described, but higher than that observed in the general population in our country (0.03%). The high frequency of DQ2 haplotype observed in patients with CC/LC confirms the existence of a high genetic susceptibility to CS in these patients, and suggests that class II HLA genes might be implicated in the pathogenesis of microscopic colitis.