GENETIC PREDISPOSITION FOR PRIMARY HYPOLACTASIA OF THE ADULT TYPE IN CHILDREN AND ADOLESCENTS WITH RECURRENT ABDOMINAL PAIN

Abstract

Aim: Primary hypolactasia of the adult type (HL) presents clinically as lactose intolerance (LI), a frequent cause of recurrent abdominal pain (RAP). It bears the risk of impaired bone growth due to avoidance of dairy products and thus inadequate calcium intake. Using a molecular genetic assay, genetic predisposition for HL was found in 24% of female adults in our region. There are only few data on this predisposition in children and adolescents as assessed by this method. We used it to determine genetic HL predisposition in children and adolescents with RAP to identify individuals at risk for LI and impaired bone growth. Methods: From VII-XII'04 65/220 patients with self reported RAP fulfilled the ROME II criteria for RAP (f: 38; m: 27; 25/65 < 8 yrs. 40/65 > 8 yrs.) and presented clinically with LI. The LCT genotypes CC, TC and TT were determined by an allele specific PCR-based assay (defining the LCT-[13910]-polymorphism near the lactase phlorizin hydrolyse gene), using 150 microliters of capillary blood or saliva. For compliance reasons lactose H2 breath tests were performed in the elder patients only (17/65). Results: 36/65 patients with RAP and clinical LI were CC homozygote (55.4%; f: 24, m: 12). 23/65 (35.4%; f: 12, m: 11) were TC heterozygote and 6/65 (9.2%; f: 3, m: 3) TT homozygote. 9/17 patients undergoing H2 breath tests had positive results: 7/9 had the CC-, and 2/9 the TC-genotype. Genotypes of the 8 patients with negative results were as follows: CC = 3, TC = 2, TT = 3. Summary: 90.8% of patients with RAP and clinically suspected LI had the CC or TC genotype for HL. Because these genotypes are both associated with a higher risk for osteoporosis, these patients and those with positive H2 breath tests are warranting close observation. An explanation for the negative functional test results in the 3 CC patients might be a higher individual threshold to the oral lactose load. Conclusion: The PCR-based genotyping for lactose gene polymorphisms presented might serve as a valuable screening method for paediatric patients with RAP and at risk for LI and osteoporosis that needs to be performed only once, is unexpensive, easy and feasible from minute blood and saliva volumes respectively.