[size=20px]A six-month old male is referred for evaluation of constipation and anal stenosis. Further imaging demonstrates a dysplastic sacrum and presacral mass. The father’s pelvic radiograph also shows an abnormal sacrum. His parents inquire about the likelihood of having more children with this anomaly.

 

You advise that genetic transmission of this anomaly with anal stenosis is

 

A autosomal dominant (50%).

 

B very unlikely (less than one percent).

 

C autosomal recessive (25%).

 

D Y-linked.

 

E X-linked.[/size]

B

think again my dear

A. Currarino triad

A

correct answer

A autosomal dominant (50%).

 

The scenario above describes Currarino triad or syndrome with anorectal malformation, dysplastic sacrum and presacral mass. It was first described by Guido Currarino, a pediatric radiologist, in 1981. There is considerable phenotypic variability ranging from an asymptomatic hemisacrum to the entire constellation of anomalies with a wide spectrum of anorectal malformations and presacral masses (e.g. anterior meningomyelocele, teratoma and rectal duplication). Additional associated urologic, gynecologic, neurologic and gastrointestinal anomalies have been seen.

 

It is a genetic disease with autosomal dominant inheritance due to haploinsufficiency. The involved gene lies on chromosome seven and is responsible for normal sacral and anorectal development. In 2000, it was identified as the HLXB9 homeobox gene on chromosome 7 q36. It is now referred to as the motor neuron and pancreas homeobox MNX1 mapped to 7q36.3. This gene encodes for the nuclear protein homeodomain-containing transcription factor. It may result from either a point mutation or deletion of the entire sequence. Approximately 50% of cases result from familial transmission whereas the remainder represent sporadic mutations. In suspected cases, it is very important to take a careful family history given the autosomal dominant nature of this disorder. The presence of the abnormal sacrum in the parent described above would suggest familial inheritance.