Avoiding pitfalls in molecular genetic testing: case studies of high-resolution array comparative genomic hybridization testing in the definitive diagnosis of Mowat-Wilson syndrome

A novel interstitial deletion of chromosome 2q21.1-q23.3: Case report and literature review

Background

Interstitial deletions of 2q are rare. Those that have been reported show varying clinical manifestations according to the size of the deletion and the genomic region involved.

Method and Results

We describe a preterm male harboring a novel interstitial deletion encompassing the 2q21.2‐q23.3 region of 2q, a deletion that has not been described previously. The patient had multiple congenital anomalies including agenesis of the corpus callosum, congenital cardiac defects, bilateral hydronephrosis, spontaneous intestinal perforation, hypospadias and cryptorchidism, sacral dimple and rocker‐bottom feet. Array comparative genomic hybridization (aCGH) analysis revealed a de novo >18 Mb deletion at 2q21.1–q23.3, a region that included (605802, 611472 and 604593) OMIM genes.

Conclusion

To the best of our knowledge this is the first report of a de novo interstitial deletion at 2q21.1–q23.3 in which haploinsufficiency of dose‐sensitive genes is shown to contribute to the patient's phenotype.

Hirschsprung's disease in children with Mowat-Wilson syndrome

BACKGROUND

Hirschsprung's disease (HSCR) is cited as a classical component in the constellation of features found in children with Mowat-Wilson syndrome (MWS), which is caused by a mutation of the ZEB2 gene. The prevalence and phenotype of HSCR in those with MWS has yet to be determined. Similarly, it is not known if children with MWS who undergo a curative pull-through operation experience similar functional outcomes. We aimed to delineate the clinical features of those with MWS and HSCR and to determine if these patients experience unfavourable outcomes following pull-through surgery.

METHODS

A systematic review of the literature using the key search term "Mowat Wilson" was performed using three online databases. Clinical data were collected on all patients with a diagnosis of MWS confirmed by ZEB2 analysis. Data regarding bowel function in children with biopsy-proven HSCR were recorded where available. Statistical analysis was performed using SPSS (v. 20.0).

RESULTS

Fifty-two articles were reviewed in the final analysis, incorporating data on 256 patients with a diagnosis of MWS. HSCR was diagnosed in 111 patients (43.4%). Males with HSCR had a slightly increased risk of genital tract anomalies (e.g. hypospadias) compared to those without HSCR (RR 1.79, p = 0.05). Data pertaining to disease phenotype and functional outcome were only available on 42 and 13 patients, respectively. Rectosigmoid aganglionosis was the most common sub-type of HSCR, being described 26 patients (66.7%), albeit accounting for a lower proportion than would normally be expected in an HSCR population. Only two patients (15.4%) were described as having normal bowel function at follow-up with the remainder having terminal stomas, or experiencing troublesome persistent bowel symptoms and recurrent enterocolitis.

CONCLUSION

Hirschsprung's disease is present in approximately 45% of patients diagnosed with MWS. Although there is a relative lack of data available on the clinical phenotype of HSCR in this group and their functional outcome following pull-through operation, our data suggest an increased prevalence of long-segment aganglionosis and an increased risk of clinically significant persistent bowel symptoms following pull-through surgery, in many cases necessitating terminal stoma formation.

CHARGE-like presentation, craniosynostosis and mild Mowat-Wilson Syndrome diagnosed by recognition of the distinctive facial gestalt in a cohort of 28 new cases

Mowat-Wilson syndrome (MWS) is characterized by moderate to severe intellectual disability and distinctive facial features in association with variable structural congenital anomalies/clinical features including congenital heart disease, Hirschsprung disease, hypospadias, agenesis of the corpus callosum, short stature, epilepsy, and microcephaly. Less common clinical features include ocular anomalies, craniosynostosis, mild intellectual disability, and choanal atresia. These cases may be more difficult to diagnose. In this report, we add 28 MWS patients with molecular confirmation of ZEB2 mutation, including seven with an uncommon presenting feature. Among the "unusual" patients, two patients had clinical features of charge syndrome including choanal atresia, coloboma, cardiac defects, genitourinary anomaly (1/2), and severe intellectual disability; two patients had craniosynostosis; and three patients had mild intellectual disability. Sixteen patients have previously-unreported mutations in ZEB2. Genotype-phenotype correlations were suggested in those with mild intellectual disability (two had a novel missense mutation in ZEB2, one with novel splice site mutation). This report increases the number of reported patients with MWS with unusual features, and is the first report of MWS in children previously thought to have CHARGE syndrome. These patients highlight the importance of facial gestalt in the accurate identification of MWS when less common features are present.