The study’s goal was to find and describe sucrase-isomaltase (SI) gene variations in non-Hispanic white paediatric and young adult patients with functional gastrointestinal disorders (FGIDs) and aberrant sucrase activity on histologically normal duodenal biopsies. Clinical symptoms and disaccharidase activity data for an aberrant sucrase activity group, as well as two normal sucrase activity groups with moderate and high sucrase activities, were obtained. Next-generation sequencing of DNA from formalin-fixed paraffin-embedded tissues of these individuals revealed SI gene mutations. The symptoms of FGIDs based on Rome IV criteria, as well as the following clinical care of aberrant sucrase activity patients with pathogenic SI gene mutations, were investigated. Thirteen SI gene variations were revealed to be substantially greater in abnormal sucrase cases with FGIDs symptoms as compared to those with moderate or high sucrase. Only 10 of the anomalous sucrase instances had clinical treatment data, and only 10 were appropriately identified and handled by physicians. The aberrant sucrase group had both lactase deficiency and pan-disaccharidase deficiency.

Heterozygous and compound heterozygous SI gene mutations were more common in patients with aberrant sucrase activity, FGIDs, and normal histology. This implies that heterozygous pathogenic variations of congenital sucrase-isomaltase deficiency might manifest as FGIDs. Lactase or pan-disaccharidase deficiency was prevalent in cases of aberrant sucrase caused by SI gene mutations.