Broadening the phenotypic spectrum of EVEN-PLUS syndrome through identification of HSPA9 pathogenic variants in the original EVE dysplasia family and two sibs with milder facial phenotype

Prenatal to preimplantation genetic diagnosis of a novel compound heterozygous mutation in HSPA9 associated with Even-Plus syndrome

BACKGROUND

Heat shock protein family A member 9 (HSPA9) prevents unfolded and dysfunctional protein accumulation, with genetic variants known to be pathogenic. Here, we determined the genetic cause of Even-Plus syndrome (OMIM: 616854) in a Chinese family.

METHODS

We collected samples from two affected and two normal individuals. Whole-exome sequencing was performed to identify their genetic profiles. Potential variants were validated using Sanger sequencing. Assisted reproduction with mutation-free embryos successfully blocked the transmission of mutations.

RESULTS

We identified novel inherited pathogenic complex heterozygous variations in the HSPA9 gene in the two affected fetuses. Three-dimensional spatial simulation of the HSPA9 protein after prediction of the mutated RNA splicing pattern abolished part of the substrate-binding domain of the protein. According to ACMG guidelines, c. 1822-1G>A and c. 1411-3T>G were classified as pathogenic and likely pathogenic, respectively. Mutation-free embryos were selected for transplantation and reconfirmed to possess no mutations. A healthy daughter was successfully born into the family.

CONCLUSIONS

This study is the first to report complex heterozygous variations in the HSPA9 gene that influence alternative splicing in early pregnancy. Our findings expand on the mutational spectrum leading to Even-Plus syndrome and provide a basis for genetic counseling and future embryonic studies.

A new phenotype of EVEN-PLUS syndrome in a Chinese family and literature review

BACKGROUND

Epiphyseal, Vertebral, Ear, and Nose (EVEN)-PLUS syndrome is a rare condition characterized by the involvement of the Epiphyses, Vertebrae, Ears, and Nose, plus other associated findings, due to pathogenic variants in the HSPA9 gene. Due to the sparse number of patients, the clinical phenotypic spectrum is not clear.

METHODS

We report two patients with pathogenic HSPA9 variants from a Chinese family. Besides the core clinical features of EVEN-PLUS syndrome, the two cases had seizures, developmental delay, and basal ganglia lesions in cerebral MRI. We also reviewed the previously published reports of patients with biallelic pathogenic HSPA9 variants.

RESULTS

Together with the presented cases, 12 cases (9 females) were identified from 6 relevant research items for analysis. All patients had synophrys or arched eyebrows, hypoplastic or dysplastic ears, hypoplastic nasal bone, and dysplastic femoral head. Other specific craniofacial features (such as triangular nares), abnormal skeletal presentations (such as bifid femur, dysplastic epiphyses at the knee, dysplastic acetabula, delayed ossification, short stature, vertebral clefting, scoliosis, and dislocated patellae), congenital heart defects, and renal alterations are common clinical features. Two patients had seizures and basal ganglia lesions in cerebral MRI. Infrequent features, such as aplasia cutis, short thorax and sternum, and widely spaced nipples, are also observed in the syndrome. Thirteen variants associated with EVEN-PLUS syndrome have been reported.

CONCLUSIONS

HSPA9 gene mutations should be suspected in all cases with specific craniofacial features, abnormal skeletal presentations, congenital heart defects, and renal alterations. Seizures and basal ganglia lesions are a new phenotype of EVEN-PLUS syndrome.