Frequency of Congenital Sucrase-Isomaltase Deficiency by Whole Exome Sequencing: Is It Really Rare?

Aim: Congenital sucrase-isomaltase deficiency (CSID) is an autosomal recessive disease with a mutation in the sucrase-isomaltase (SI) gene and disaccharide maldigestion. With limited data, the estimated incidence of this disease is 57.59/10⁶ births and its heterozygosity rate is 1/132. We aimed to evaluate cases who underwent whole exome sequencing (WES) analysis in the medical genetics unit with regards to the frequency and clinic of CSID. Materials and Methods: The patients’ files who underwent WES between 2018-2023 were evaluated retrospectively. The demographic characteristics, complaints, physical examination, and laboratory findings of those patients with SI gene mutations were recorded. Cases with mutations were recontacted and symptom questioning was performed. Results: Mutations were detected in 25 (8.3%) of 300 patients who underwent WES analysis. One case had a compound heterozygous mutation, while 24 cases were heterozygous. The mean age was 22.4±17.6 years (1.8-52 years) and 16 (64%) were females. Nine of the cases (36%) were symptomatic. Conclusion: Data on the frequency of CSID are insufficient and variable in the literature. The SI heterozygosity rate in our study was higher than some studies. There were similar rates when compared to the study conducted on symptomatic pediatric patients in our country. Although the data of our study includes a heterogeneous group to evaluate the frequency of CSID, it consists of a group with suspected genetic diseases rather than healthy individuals. Therefore, large-scale population-based studies are needed.