[Application of next generation sequencing in 3 Waardenburg syndrome]

Clinical application of whole exome sequencing technology in small-for-gestational-age children

AIM

To apply whole exome sequencing (WES) for molecular diagnosis of small-for-gestational-age (SGA) children.

METHODS

We retrospectively analyzed the data of 60 SGA children in our hospital, and performed developmental assessment, laboratory tests, imaging tests, and whole exome sequencing (WES), which were combined with clinical phenotypes to clarify the pathogenicity of the variant genes in the children.

RESULTS

Sixty SGA children were tested, and pathogenic SGA was detected at relatively high frequencies on chromosomes 7, 8, and 22. Of these, karyotype analysis clearly suggested developmental disorders in 4 patients. Also, a case of Wiedemann-Steiner syndrome due to a de novo nonsense variant in the KMT2A gene was detected.

CONCLUSIONS

The use of WES testing technology to increase the diagnosis rate of children with special SGA is conducive to the correct diagnosis and treatment of such children.

[Analysis of molecular genetics and clinical characteristics of 3 children with Waardenburg syndrome]

Objective:To analyze the molecular genetics and clinical characteristics of 3 children with syndromic deafness were analyzed to clarify their causative genes and genetic characteristics. Methods:The medical records of 3 children and their parents were collected and analyzed, including physical examination, hearing evaluation, temporal bone CT, and cranial MRI. Whole-exome sequencing（WES） was used to screen for pathogenic gene variants, and Sanger sequencing was used to verify the candidate positive variants in the probands and their parents. Results:All 3 patients were female with normal intelligence. Patient 1 and 3 had a family history of deafness, which conformed to the pattern of autosomal dominant inheritance. All three patients had bilateral profound sensorineural hearing impairment with bright-blue sclera. Other phenotypes included hypertelorism（patient 1）, multiple dyschromatosis（patient 2）, and yellowish hair（patient 2）, blepharoptosis（patient 3）. Patient 3 had bilateral vestibular enlargement, internal auditory canal enlargement, and bilateral inner ear malformations. Mother of patient 1 had only left mild hearing impairment; mother of patient 3 had bilateral hearing impairment with unilateral bright-blue sclera and yellowish hair. WES detected heterozygous variants, PAX3 c.811C>T, MITF c.632T>C, and SOX10 c.1359_1360 insGCCCCACA, in patient 1, 2, and 3, respectively. The variants in patient 1 and 3 were inherited from their mothers who had hearing impairment, and MITFvariant in patient 2 may be a spontaneous variation. The final diagnoses were that patient 1 with Waardenburg syndrome type 1（WS1）, and the mother of patient 1, patient 2, patient 3, and the mother of patient 3 with WS2. Conclusion:WS is a syndromic deafness, and the main clinical features include autosomal dominant inheritance and scleral pigment abnormalities. However, the findings of this study show that there is still phenotypic heterogeneity in WS even caused by the same gene variant, so it depends on genetic tests to confirm the diagnosis; The gene variant of patient 1 and 2 was never been reported in other patients, which expands the pathogenic variant spectrum of WS.