Wiedemann–Steiner syndrome (WDSTS) is a rare genetic disorder characterized by facial gestalt, neurodevelopmental delay, skeletal anomalies and growth retardation, which is caused by variation of KMT2A gene. To date, only 2 Chinese WDSTS patients have been reported. Here, we report the phenotypes and KMT2A gene variations in 14 unrelated Chinese WDSTS patients and investigate the phenotypic differences between the Chinese and French cohorts. Next generation sequencing was performed for each patient, and the variants in the KMT2A gene were validated by Sanger sequencing. The phenotypes of 16 Chinese WDSTS patients were summarized and compared to 33 French patients. Genetic sequencing identified 13 deleterious de novo KMT2A variants in 14 patients, including 10 truncating, 2 missenses and 1 splicing variants. Of the 13 variants, 11 are novel and two have been reported previously. One of the patients is mosaic in the KMT2A gene. The variation spectra and phenotypic profiles of the Chinese WDSTS patients showed no difference with patients of other ethnicities; however, differ in the frequencies of several clinical features. We demonstrated that variations in the KMT2A gene can lead to both advanced and delayed bone age. We identified 6 novel phenotypes, which include microcephaly, deep palmar crease, external ear deformity, carpal epiphyseal growth retardation, dyslipidemia, and glossoptosis. In addition, patients harbored missense variants in the CXXC zinc finger domain of KMT2A showed more severe neurophenotypes. Our study consists of the largest cohort of Chinese WDSTS patients that continues to expand the WDSTS phenotypic and variation spectrum. Our results support the notion that the CXXC zinc finger domain of KMT2A gene is a hotspot for missense variants associated with more severe neurophenotypes.

Fructose-1,6-bisphosphatase (FBPase) deficiency is a rare, autosomal recessive inherited disease caused by the mutation of the FBP1 gene, the incidence is estimated to be between 1/350,000 and 1/900,000. The symptoms of affected individuals are non-specific and are easily confused with other metabolic disorders. The present study describes the clinical features of four Chinese pediatric patients who presented with hypoglycemia, hyperlactacidemia, metabolic acidosis, and hyperuricemia. Targeted-next generation sequencing using the Agilent SureSelect XT Inherited Disease Panel was used to screen for causal variants in the genome, and the clinically-relevant variants were subsequently verified using Sanger sequencing. Here, DNA sequencing identified six variations of the FBP1 gene (NM_000507.3) in the four patients. In Case 1, we found a compound heterozygous mutations of c.704delC (p.Pro235GlnfsX42) (novel) and c.960_961insG (p.Ser321Valfs) (known pathogenic). In Case 2, we found a compound heterozygous mutations of c.825 + 1G>A and c.960_961insG (both were known pathogenically). In Case 3, a homozygous missense mutation of c.355G>A (p.Asp119Asn) (reported in ClinVar database without functional study) was found. Case 4 had a compound heterozygous mutations c.720_729del (p.Tyr241GlyfsX33) (novel) and c.490G>A (p.Gly164Ser) (known pathogenically). Further in vitro studies in the COS-7cell line demonstrated that the mutation of ASP119ASN had no impact on protein expression, but decreased the enzyme activity, and with which the clinical significance of Asp119Asn can be determined to be likely pathogenic. This report not only expands upon the known spectrum of variation of the FBP1 gene, but also deepens our understanding of the clinical features of FBPase deficiency.

Aldosterone synthase deficiency (ASD) is a rare, autosomal recessive inherited disease. Mutations in the CYP11B2 gene are responsible for the occurrence of ASD, and the clinical manifestations of ASD vary with age. Affected infants may develop symptoms of mineralocorticoid deficiency, including clinical presentation with frequent vomiting, a variable degree of hyponatremia, hyperkalemia, and metabolic acidosis combined with poor growth, which are easily confused with several other endocrine genopathies, including pseudohypoaldosteronism type 1 and congenital adrenal hyperplasia. In the present study, whole exome sequencing (WES) was used to screen for causal variants in the genome of a Chinese pediatric patient with confusing endocrine disorder symptoms. Clinical symptoms of frequent vomiting, hyponatremia and hyperkalemia were selected as the filtering indices to analyze the WES data. Clinically relevant variants were subsequently verified using Sanger sequencing. Minigene construct analysis was used to assess the consequence of a splicing variant in the CYP11B2 gene. The compound heterozygous mutations, c.1009C>T and c.240‑1G>A, in the CYP11B2 gene were identified and confirmed, and represented novel variants. Sequence analysis results revealed that the c.1009C>T mutation at codon 337 of exon 6 was a nonsense mutation, which led to early termination of the protein translation process. In addition, further investigation of the splicing pattern in a minigene construct showed that the c.240‑1G>A mutation led to the preservation of intron 1, with the 3'‑splice site disappearing during transcriptional processing of the mRNA. Using molecular genetic assessments, the patient was finally diagnosed with ASD. Therefore, the present study identified two novel CYP11B2 gene mutations in a Chinese patient with ASD, indicating exome sequencing as an effective diagnostic tool for rare endocrine-metabolic diseases.