Adult-type hypolactasia: Clinical, morphologic and functional characteristics in Brazilian patients at a university hospital

Background: Adult-type hypolactasia (AH) is the most common form of disaccharidase deficiency in humans, with a prevalence that varies among ethnic groups. In Brazil, the few available studies suggest a high prevalence of this condition. The objective of this study was to determine the prevalence of AH in Brazilian patients at the Ribeirao Preto University Hospital, and to study its morphologic and functional expression. Methods: One hundred fifteen patients between 5 and 60 years undergoing upper gastrointestinal endoscopy were included. Mucosal biopsy specimens were obtained from the second portion of the duodenum. AH was defined by the disaccharidase activity (lactase/sucrase ratio) of the duodenal mucosa. The morphologic expression of lactase was studied by immunohistochemistry. Results: The mean age of the subjects was 28.8 +/- 14.8 years. Seventy of the 115 subjects (60.8% prevalence) had AH by enzyme activity measurements. Milk drinking was common and similar in patients with and without AH. Among the patients, 91.3% of the nonwhite and 53.2% of the white individuals had hypolactasia (P = 0.002). Immunohistochemistry revealed the presence of lactase in 73.3% of individuals with normal lactase activity. Two different expression patterns were found in patients with AH. Conclusions: The prevalence of AH was high in our subjects and similar to that reported in other Brazilian studies. Hypolactasia was more common among nonwhites. Immunohistochemistry permitted the identification of two phenotypes of AH, the first characterized by the absence of both stainable lactase and lactase activity, and the second by the presence of stainable lactase without significant activity.