Brachytelephalangic chondrodysplasia punctata caused by new small hemizygous deletion in a boy presenting with hearing loss

A novel frameshift deletion variant of ARSL associated with X-linked recessive chondrodysplasia punctata 1: a case report and literature review of prenatal, confirmed cases

BACKGROUND

X-linked recessive chondrodysplasia punctata 1 (CDPX1) is a rare congenital skeletal dysplasia characterized by stippled epiphyses, nasal hypoplasia, and brachytelephalangy. ARSL (formerly known as ARSE), a member of the sulfatase gene family located on Xp22.3, has been identified as the causative gene for CDPX1. The high clinical and genetic heterogeneity of CDPX1 presents a challenge to prenatal diagnosis.

CASE PRESENTATION

A G1P0 woman in her 30s with an unremarkable prenatal course presented in the second trimester. Maternal diseases, tobacco, alcohol, and drug history during pregnancy were denied. Obstetrical ultrasound examination revealed a flattened nose and a flattened midface with echogenic alterations of lumbar spinous process in the fetus. Amniocentesis was performed for genetic testing. A normal karyotype and a negative result of CNV-seq were obtained. However, Whole exome sequencing (WES) in trios revealed a hemizygous ARSL variant [NM_000047.3:c.1108del p.(Trp370Glyfs*35)] in the fetus, which was maternally inherited as confirmed by Sanger sequencing. This variant was absent from the genomAD and HGMD databases. According to the ACMG guidelines, this variant was interpreted as likely pathogenic (PVS1 + PM2_Supporting). The couple decided to terminate the pregnancy. After induction of labour, a severe nasal hypoplasia was noted; and brachytelephalangy was not remarkable. Postmortem digital X-ray imaging revealed symmetrical stippled epiphyses of the vertebrae in all spine regions and enlargement of spinous process of L1-L4 vertebrae.

CONCLUSION

A novel frameshift deletion variant of ARSL and the associated fetal phenotype have been identified. This study provides useful information for prenatal diagnosis and genetic counseling of CDPX1.

Chromosome Xp22.3 deletion syndrome with X-linked ichthyosis, Kallmann syndrome, short stature, generalized epilepsy, hearing loss, attention deficit hyperactivity disorder, and intellectual disability – A rare report with review of literature

Chromosome Xp22.3 deletion syndrome is a very rare contiguous gene deletion syndrome with variable phenotype due to the deletion of genes from the distal short arm of the X chromosome (Xp), including the short-stature homeobox (SHOX), anosmin-1 (ANOS1), arylsulfatase (ARSL), neuroligin-4 (NLGN4), and steroid sulfatase (STS) genes. We have reviewed the available literature on the chromosome Xp22.3 deletion syndrome. A 10-year-old boy presented with global developmental delay, generalized epilepsy, decreased hearing, and hyperactivity. He had no significant family history. Examination revealed microcephaly, short stature, and dry and scaly skin lesions on the trunk. He had thick arched eyebrows, a depressed nasal bridge, a long philtrum, high arched palate, retrognathia, brachytelephalangy, brachymetatarsia, and mild scoliosis. Brainstem-evoked response audiometry testing revealed moderate hearing loss. Magnetic resonance imaging showed cerebellar tonsillar ectopia. Clinical exome sequencing revealed a likely pathogenic contiguous deletion (~8.10 Mb) spanning genomic location chrX:g.(_630898)_(8732037_)del encompassing ANOS1, ARSL, NLGN4X, SHOX, and STS genes. We have reviewed the available literature for reported associations of Chromosome Xp22.3 deletion syndrome and report a novel association of X-linked ichthyosis, Kallmann syndrome, global developmental delay, short stature, bilateral hearing loss, generalized epilepsy, attention deficit hyperactivity disorder, and intellectual disability.

Uniparental disomy as a mechanism for X-linked chondrodysplasia punctata

We describe a female infant with X-linked chondrodysplasia punctata (CDPX1) as a result of maternal isodisomy of the X chromosome. Targeted Sanger sequencing and targeted next-generation sequencing of ARSL were used to test for the familial variant. This patient was homozygous for ARSL NM_000047.2: c.1227_1228delinsAT p.(Ser410Cys) familial variant, consistent with a diagnosis of CDPX1. Uniparental disomy is a type of chromosomal variation. Although not necessarily pathogenic, it can cause imprinting disorders and X-linked recessive disorders in females, and be a cause of autosomal recessive conditions when only one parent is a carrier. The patient described highlights that uniparental disomy can be a rare cause of X-linked recessive conditions. This mode of inheritance has not been previously described in this condition.

Prenatal Diagnosis in a Fetus With X-Linked Recessive Chondrodysplasia Punctata: Identification and Functional Study of a Novel Missense Mutation in ARSE

X-Linked recessive chondrodysplasia punctata (CDPX1) is a rare skeletal dysplasia characterized by stippled epiphyses, brachytelephalangy, and nasomaxillary hypoplasia. CDPX1 is caused by function loss of arylsulfatase E (ARSE, also known as ARSL). Pathogenic mutations in ARSE are responsible for CDPX1 in newborns or adults; however, studies have not fully explored prenatal cases. In the current study, a novel missense mutation (c.265A > G) in ARSE was identified in a fetus with short limbs using whole-exome sequencing (WES). Bioinformatic analysis showed that the variant was pathogenic, and RT-qPCR, Western blot, and enzymatic assays were performed to further explore pathogenicity of the variant. The findings showed that the variant decreased transcription and protein expression levels and led to loss of enzymatic activity of the protein. The novel mutation c.265A > G in ARSE was thus the genetic cause for the phenotype presented by the fetus. The current study presents a prenatal case in Chinese population using functional analysis of ARSE, which helps the family to predict recurrence risks for future pregnancies and provides more information for understanding this rare condition. The findings show that WES is a feasible method for prenatal diagnosis of fetuses with CDPX1.