Second instance of co-occurring 22q11.2 deletion syndrome and Williams syndrome

We present an 18-month-old male with Tetralogy of Fallot, retrognathia, short stature, global developmental delay, and dysmorphic features who was found to have dual diagnoses of both Williams syndrome and 22q11.2 deletion syndrome (22q11.2DS). To our knowledge, this is the second case of such a co-occurrence documented in the medical literature. Our patient presents with a blended physical phenotype of these two conditions and a behavioral phenotype that is distinct from what is typically observed in either disorder alone. We compare our patient's phenotype to the previously reported case and to the typical phenotypes for each individual condition. Additionally, we discuss why the occurrence of these two disorders together seems to be so rare, and the benefit of a genetics evaluation to an inpatient service team and the patient.

A de novo 2.2 Mb recurrent 17q23.1q23.2 deletion unmasks novel putative regulatory non-coding SNVs associated with lethal lung hypoplasia and pulmonary hypertension: a case report

BACKGROUND

Application of whole genome sequencing (WGS) enables identification of non-coding variants that play a phenotype-modifying role and are undetectable by exome sequencing. Recently, non-coding regulatory single nucleotide variants (SNVs) have been reported in patients with lethal lung developmental disorders (LLDDs) or congenital scoliosis with recurrent copy-number variant (CNV) deletions at 17q23.1q23.2 or 16p11.2, respectively.

CASE PRESENTATION

Here, we report a deceased newborn with pulmonary hypertension and pulmonary interstitial emphysema with features suggestive of pulmonary hypoplasia, resulting in respiratory failure and neonatal death soon after birth. Using the array comparative genomic hybridization and WGS, two heterozygous recurrent CNV deletions: ~ 2.2 Mb on 17q23.1q23.2, involving TBX4, and ~ 600 kb on 16p11.2, involving TBX6, that both arose de novo on maternal chromosomes were identified. In the predicted lung-specific enhancer upstream to TBX4, we have detected seven novel putative regulatory non-coding SNVs that were absent in 13 control individuals with the overlapping deletions but without any structural lung anomalies.

CONCLUSIONS

Our findings further support a recently reported model of complex compound inheritance of LLDD in which both non-coding and coding heterozygous TBX4 variants contribute to the lung phenotype. In addition, this is the first report of a patient with combined de novo heterozygous recurrent 17q23.1q23.2 and 16p11.2 CNV deletions.