Whole exome sequencing of sporadic patients with Currarino Syndrome: A report of three trios

Currarino syndrome: a comprehensive genetic review of a rare congenital disorder

Background

The triad of a presacral mass, sacral agenesis and an anorectal anomaly constitutes the rare Currarino syndrome (CS), which is caused by dorsal–ventral patterning defects during embryonic development. The major causative CS gene is MNX1, encoding a homeobox protein.

Main body

In the majority of patients, CS occurs as an autosomal dominant trait; however, a female predominance observed, implies that CS may underlie an additional mode(s) of inheritance. Often, the diagnosis of CS is established solely by clinical findings, impacting a detailed analysis of the disease. Our combined data, evaluating more than 60 studies reporting patients with CS-associated mutations, revealed a slightly higher incidence rate in females with a female-to-male ratio of 1.39:1. Overall, MNX1 mutation analysis was successful in only 57.4% of all CS patients investigated, with no mutation detected in 7.7% of the familial and 68% of the sporadic patients. Our studies failed to detect the presence of an expressed MNX1 isoform that might explain at least some of these mutation-negative cases.

Conclusion

Aside from MNX1, other genes or regulatory regions may contribute to CS and we discuss several cytogenetic studies and whole-exome sequencing data that have implicated further loci/genes in its etiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01799-0.

Laparoscopic-Assisted Anorectal Pull-Through for Currarino Syndrome

Objective: Currarino syndrome (CS) is characterized by the triad of sacral anomalies, presacral tumor, and anorectal malformation (ARM). This study evaluates the feasibility and outcomes of laparoscopic-assisted anorectal pull-through (LAARP) for CS. Materials and Methods: Children admitted for primary or redo repair of CS through LAARP between 2016 and 2019 were reviewed. The indication of redo included constipation with megarectosigmoid, residual presacral mass, anastomosis leak, and secondary fistula. ARM was corrected by excision of rectal stenosis, fistula, and its associated megarectosigmoid. This was followed by a complete surgical resection of the presacral tumor, with subsequent pull-through and anocolic anastomosis. This was done with a combined laparoscopic and transanal approach. The detailed surgical techniques, early postoperative complications, and mid-term functional outcomes were summarized. Results: Fourteen patients underwent LAARP for primary (N = 4) and redo (N = 10) repair of CS. Four of them had colostomy previously. Mean age at operation was 20.7 ± 13.9 months. Mean operative time was 120 ± 25 minutes. Median hospital stay was 8 days (range 7-9 days) postoperatively. None of the patients developed early postoperative complications such as anastomotic leaks, presacral abscesses, recurrent fistulas, and residual mass. Bowel function was assessed 1 year after LAARP in 10 patients. Mean follow-up time was 15.9 months. The frequency of bowel movements was 3.3 ± 1.5/day. Constipation occurred in 2 patients. Occasional soiling (<3 times/week) was reported in 4 patients and frequent soiling (>3 times/week) was in 1. Conclusion: LAARP for CS is safe and effective.

Spectrum of MNX1 Pathogenic Variants and Associated Clinical Features in Korean Patients with Currarino Syndrome

BACKGROUND

The major genetic cause of Currarino syndrome (CS), a congenital malformation syndrome typically characterized by sacral agenesis, anorectal malformation, and presence of a pre-sacral mass, is known to be pathogenic variants in motor neuron and pancreas homeobox 1 (MNX1), which exist in almost all familial cases and 30% of sporadic cases. Less commonly, a large deletion or a complex rearrangement involving the 7q36 region is associated with CS. We investigated the spectrum of MNX1 pathogenic variants and associated clinical features in the Korean patients with CS.

METHODS

We enrolled 25 patients with CS, including 24 sporadic cases and one familial case. Direct sequencing of MNX1 and multiplex ligation-dependent probe amplification were performed. We also analyzed clinical phenotypes and evaluated genotype-phenotype correlations.

RESULTS

We identified six novel variants amongst a total of six null variants, one missense variant, and one large deletion. The null variants included four frameshift variants (p.Gly98Alafs* 124, p.Gly145Alafs*77, p.Gly151Leufs*67, and p.Ala216Profs*5) and two nonsense variants (p.Tyr186* and p.Gln212*). The missense variant, p.Lys295Gln, was located in the highly-conserved homeobox domain and was predicted to be deleterious. A large deletion involving the 7q36 region was detected in one patient. Pathogenic variants in MNX1 were detected in 28% of all CS cases and 25% of sporadic cases. The clinical phenotype was variable in patients with and without pathogenic variants; no significant genotype-phenotype correlation was observed.

CONCLUSIONS

This study revealed the spectrum and phenotypic variability of MNX1 pathogenic variants in the Korean population.