Currarino syndrome at Rikshospitalet 1961-2012

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.

Novel MNX1 mutations and genotype-phenotype analysis of patients with Currarino syndrome

BACKGROUND

Currarino syndrome (CS) is a specific complex of congenital caudal anomalies, including anorectal malformations, presacral mass and sacral anomalies. Mutations in the MNX1 gene are closely related to CS and occur in almost all familial cases and less than half of sporadic patients. We investigated the spectrum of MNX1 pathogenic variants and associated clinical features in Chinese patients with CS.

RESULTS

Seventeen index patients from 16 families were recruited from 2015 to 2018. All patients were diagnosed with CS and treated at the Capital Institute of Pediatrics Affiliated Children's Hospital. Genetic testing was applied to identify mutations in CS patients and their relatives by whole-exome sequencing and Sanger sequencing. Functional verification was performed for a recurrent noncanonical splice site variant in MNX1 with a minigene splicing assay. In 17 CS patients, 14 were complete CS and 3 were mild CS. Nine variants in MNX1 were identified in 11 patients, and these included two frameshift mutations (p.Leu223Leufs*61, p.X402Serfs*70), four nonsense mutations (p.Gly42X, p.Cys88X, p.Gln24X, p.Cys241X), one missense mutation (p.Trp288Leu), one splice region variant (c.691 + 3G > T) and one polyalanine polymorphism (p.Ala135insAlaAla). Seven of these nine variants have never been reported. Pathogenic MNX1 mutations were found in 100% (4/4) of familial and 46% (6/13) of sporadic patients.

CONCLUSION

Our study expanded the mutation spectrum of MNX1 and provided clinical and genetic analyses of seventeen CS patients from mainland China.

Currarino syndrome and microcephaly due to a rare 7q36.2 microdeletion: a case report

BACKGROUND

Currarino syndrome is a rare condition characterized by presacral mass, anorectal malformation and sacral dysgenesis.

CASE PRESENTATION

We report the case of a child that presented chronic constipation, encopresis and mycrocephaly. The characteristics were initially compatible with a case of functional constipation and a therapy with polyethylene glycol was prescribed. After a year, because of poor response, a plain abdominal X-ray was performed, detecting sacrum abnormalities. Finally, a CGH-array analysis was performed and a form of Currarino Syndrome caused by a rare 7q36 microdeletion, was diagnosed.

CONCLUSION

Occult spinal dysraphism should be suspected in case of poor polyethylene glycol responder constipation, even when evident sacral abnormalities on the physical examination are not detected.

Currarino syndrome: does the presence of a genetic anomaly correlate with a more severe phenotype? A multicentre study

BACKGROUND/PURPOSE

Currarino syndrome (CS) phenotype, initially described as the triad of hemisacrum, anorectal malformation (ARM) and presacral mass, can be extremely variable. The triad is often incomplete and 3 main CS phenotypical subtypes have been described: Complete, Mild and Minimal. Various associated malformations are often present. Mutations in the MNX1 gene are the main genetic background of CS, although they are not present in almost half of the cases. Aim of our study is to analyze the distribution of the 3 CS subtypes and the incidence of associated malformations in a large sample of patients and to add information about the role of the genetic testing in guiding the diagnostic and prognostic evaluation of CS patients.

METHODS

A multicentre retrospective data collection was performed. CS patients' phenotype was accurately analyzed according to a diagnostic-therapeutic standardized data collection sheet. The distribution of the three CS types and the frequency of each associated malformation were calculated. The phenotype of the patients with a known genetic anomaly was compared to the phenotype of the population with no genetic diagnosis, in order to determine whether the presence of a known genetic defect could correlate with a more severe CS phenotype.

RESULTS

Data from 45 patients were analyzed. Twenty patients (44.5%) presented a Complete CS type, 19 (42.2%) a Mild CS and 6 (13.3%) a Minimal CS. In addition to the classical triad elements, 38 (84.5%) patients showed associated anomalies. The group of patients who resulted positive for a MNX1 mutation comprised a higher number (56.5%) of Complete CS cases than the group of patients that did not carry any MNX1 mutation (13%) (p = 0.0085). We could not find any relationship between CS subtype and the number of associated anomalies (p = 0.5102).

CONCLUSIONS

The presence of a MNX1 mutation seems to correlate with a more severe CS phenotype. MNX1 seems the main responsible for the expression and the severity of the CS triad, while the associated anomalies appear to be prevalently determined by genes sited on different loci. A thorough multidisciplinary diagnostic overview of CS patients should always include genetic counseling and analysis, both in postnatal and prenatal settings.

TYPE OF STUDY

Retrospective Study.

LEVEL OF EVIDENCE

II.

Phenotype analysis impacts testing strategy in patients with Currarino syndrome

Currarino syndrome (OMIM 175450) presents with sacral, anorectal, and intraspinal anomalies and presacral meningocele or teratoma. Autosomal dominant loss-of-function mutations in the MNX1 gene cause nearly all familial and 30% of sporadic cases. Less frequently, a complex phenotype of Currarino syndrome can be caused by microdeletions of 7q containing MNX1. Here, we report one familial and three sporadic cases of Currarino syndrome. To determine the most efficient genetic testing approach for these patients, we have compared results from MNX1 sequencing, chromosomal microarray, and performed a literature search with analysis of genotype-phenotype correlation. Based on the relationship between the type of mutation (intragenic MNX1 mutations vs 7q microdeletion) and the presence of intellectual disability, growth retardation, facial dysmorphism, and associated malformations, we propose a testing algorithm. Patients with the classic Currarino triad of malformations but normal growth, intellect, and facial appearance should have MNX1 sequencing first, and only in the event of a normal result should the clinician proceed with chromosomal microarray testing. In contrast, if growth delay and/or facial dysmorphy and/or intellectual disability are present, chromosomal microarray should be the first method of choice for genetic testing.