Segmental maternal uniparental disomy of chromosome 7q in a patient with congenital chloride diarrhea

Abstract

Background: The main symptoms of congenital chloride diarrhea (CCD) main symptoms are watery diarrhea, hypochloremia, and hypokalemic metabolic alkalosis. Silver-Russell syndrome (SRS) is a heterogeneous imprinting disorder characterized by severe intrauterine retardation, poor postnatal growth, and facial dysmorphism.

Methods: Parent-offspring trio whole-exome sequencing was used to identify the causal variants. Sequencing reads were mapped to the reference of human genome version hg19. Sanger sequencing was performed as a confirmatory experiment.

Results: The proband was a patient with SRS caused by maternal uniparental disomy 7. The CCD of the proband was caused by homozygous variant c.1515-1 (IVS13) G>A; both mutated alleles were inherited from her mother.

Conclusion: We report the first clinical case of CCD and SRS occurring together. Patients with milder phenotypes may be difficult to diagnose in early stage, but close monitoring of potential complications is important for identification.

Keywords: SLC26A3; Congenital chloride diarrhea; Silver-Russell syndrome; mUPD.

FIGURE 1

Clinical findings of the patient diagnosed with CCD combined with SRS. (A) Growth and weight charts. (B) Photographs of the patient at different months with triangular facial appearance and protruding forehead

FIGURE 2

Genetic test results. (A) Pedigree and SLC26A3 variant identified in the family. The proband was the only patient in the family, and harbored a SLC26A3 variant. Mother of the patient was heterozygous whereas father of the patient was wild type. (B) SNP sites sequenced on chr7 (screened by sequencing quality) indicated that at least 86.51 Mb of genome 7q11q36 (chr7: 65446986–151960086) was maternal uniparental disomy