What Is the Currarino Triad?
Currarino triad, also called Currarino syndrome, partial sacral agenesis with the intact first sacral vertebra, presacral mass, and anorectal malformation is a rare genetic autosomal dominant disorder, first described by Guido Currarino, an American radiologist, in 1981.
Currarino syndrome is characterized by a triad that consists of the following:
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Sacral agenesis abnormalities (sickle-shaped sacrum).
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Pre-sacral mass (meningocele, teratoma, hamartoma).
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Anorectal malformation (anorectal stenosis).
Very few cases present with all three abnormalities; anorectal malformations are most common amongst patients with Currarino syndrome; thus, constipation is the most common symptom.
What Are the Genes Involved?
HLXB9 HB9 is the gene involved; it has three exons and is a homeobox gene; it contains sequence-specific DNA binding proteins that control gene expression. It functions as a transcription factor regulating gene expression. Among various regions of the gene, studies suggest the cloacal plate plays an essential role in the development of the anorectum, and deficiencies cause anorectal malformation.
What Are the Causes of the Currarino Triad?
When said to have genetic etiology, any condition suggests abnormal functioning or the absence of one or more genes causing the condition.
Similarly, the Currarino triad is caused by one of the following conditions:
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Genetic changes in the MNX1 gene most often cause the Currarino triad.
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Curarine syndrome is an autosomal dominant condition; variable genes have been reported to cause a partial or incomplete form of the syndrome, which presents with the incomplete triad, the locus of the Currarino triad is found to be located on the HLXB9 homeobox gene.
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In some cases, the syndrome is found to have hereditary transmission.
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Few studies have also reported abnormalities in embryogenesis to cause the syndrome.
What Are the Symptoms of the Currarino Triad?
Currarino triad is asymptomatic in the majority of cases, but the patients who are symptomatic present with the following:
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Symptoms as a result of their renal or gynecological malformation.
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Chronic constipation, defecation problems.
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Abdominal distension.
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Vomiting.
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Hemisacrum, teratomas.
How Is the Currarino Triad Diagnosed?
The diagnosis of the disorder is accidental if the child does not present with any symptoms during childhood. The syndrome is diagnosed on a routine X-ray or MRI (magnetic resonance imaging) for other medical reasons. This syndrome varies in severity, and many instances are asymptomatic; in cases with constipation, diagnosis is made based on clinical examination, where the most common finding is the compression of the rectum by anterior sacral mass. In such instances, if the clinical findings are missed out, which can be due to missing out on digital examination, the syndrome is most likely to be misdiagnosed as some other cause of constipation, like Hirschsprung disease. The CECT (contrast-enhanced computed tomography) pelvis or MRI confirms the diagnosis.
The usual evaluation protocol should always be followed to minimize diagnostic errors. These are as follows:
Digital Rectal Examination: Thorough digital rectal examination must be done to eliminate other disorders with similar symptoms like Hirschsprung disease, anal stenosis, and any other pelvic pathology compressing the rectum.
Abdominal and Spinal Radiography: Direct abdominal and spinal radiographic examination must be carried out to analyze the fecal loading of the colon and any vertebral or sacral abnormalities.
Ultrasound Pelvis: Ultrasound of the pelvis is ordered to check for any lesions or abnormal growths in the pelvis, as it leads to compression of the rectum to cause constipation.
MRI Pelvis: In cases where ultrasound shows lesions, an MRI pelvis must be done to determine the location, extent, and association with the rectum of the lesion.
What Are the Radiological Findings?
1. Anorectal malformation or congenital anorectal stenosis.
2. Sacrococcygeal osseous defect (always present).
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Classically, the hemisacrum with the intact first sacral vertebra.
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Mild (hypoplasia) to severe (agenesis) of the sacrum and coccyx 6.
3. Presacral mass (various types).
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Anterior sacral meningocele (most common).
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Tumor (teratoma).
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A dermoid is an epidermoid cyst.
What Are the Treatments Available?
Treatment mainly aims at curing the syndrome's symptoms. Patients with symptoms at birth like imperforate anus require invasive surgical treatment; surgery is planned for the excision of presacral mass and correction of anorectal malformation.
The most common surgery performed is for pre-sacral mass, as this mass causes obstruction and symptoms of meningitis. Appropriate, timely diagnosis can identify the problem and avoid complications if appropriate treatment and care are provided during early childhood.
Surgery with chemotherapy: Recent approach in cases with malignant transformation involves a combination of surgery and chemotherapy. Chemotherapeutic agents utilized include Bleomycin, Etoposide, and Carboplatin, considered the gold standard. Some researchers suggest replacing Carboplatin with Cisplatin considering its side effects like nephrotoxicity. In patients with meningocele, it is advisable to carry out two staged surgery, as it reduces the risk of postoperative meningitis.
Some patients may develop symptoms due to their renal or gynecological malformation, which needs to be managed appropriately. Spinal cord tethering is recognized and may recur, requiring long-term surveillance. Many individuals suffer from chronic constipation. Patients with a presacral mass, particularly those with an anterior meningocele, can develop headaches if pressure increases within the abdominal cavity from coughing, sneezing, or lying on their abdomens.
What Is the Prognosis and Differential Diagnosis of the Currarino Triad?
Early diagnosis and treatment have resulted in a good prognosis for the syndrome. However, the patient struggles to lead a normal life as, in some cases, the patient can face problems like recurrence, gynecological malformations, etc. The most common risk factor that persists is malignancy.
Conclusion
Currario syndrome or currario triad is a rare genetic disorder, first described by Guido Currarino, an American radiologist, in 1981. The triad comprises a triad of symptoms that include sacral agenesis abnormalities (sickle-shaped sacrum), presacral mass (meningocele, teratoma, hamartoma), and anorectal malformation (anorectal stenosis).
All three symptoms appear in rare cases. Most cases with the syndrome are diagnosed accidentally due to their asymptomatic nature; symptomatic cases commonly face problems like constipation and headache and are diagnosed during early childhood. The syndrome is treated surgically with a good prognosis.
