Currarino syndrome is a rare, inherited congenital disorder affecting the lower back, pelvis, and anorectal region. It is characterized by a specific set of malformations that develop during early fetal life, influencing the formation of the sacrum, the lower spinal cord, and the bowel. The estimated prevalence is between 1 to 9 per 100,000 people, with a slightly higher incidence in females.
The Currarino Triad
Currarino syndrome is defined by a distinct group of three malformations, collectively known as the Currarino triad. These anomalies typically include a sacral bone defect, a presacral mass, and an anorectal malformation.
Sacral Anomaly
The sacral anomaly involves a malformation of the sacrum, the triangular bone at the base of the spine. This defect is always present in Currarino syndrome and commonly appears as a “scimitar sacrum,” a crescent-shaped deformity of the lower sacral vertebrae. The sacral defect can range from mild hypoplasia to more severe agenesis, meaning incomplete development or absence of parts of the sacrum and coccyx.
Presacral Mass
A presacral mass is a growth located in the space directly in front of the sacrum. This mass is most frequently an anterior sacral meningocele, which is a sac of cerebrospinal fluid that protrudes from the spinal canal through a defect in the sacrum. Other types of masses can include a benign tumor called a teratoma, or less commonly, dermoid/epidermoid cysts or enteric cysts. This mass can exert pressure on surrounding structures.
Anorectal Malformation
The anorectal malformation refers to structural issues affecting the anus or rectum. The most frequent manifestation is severe, chronic constipation, which can be present from birth. Other issues may include anorectal stenosis, where the anal canal is narrowed, or an anteriorly displaced anus.
Genetic Origins
Currarino syndrome is primarily caused by a mutation in a specific gene known as MNX1, previously referred to as HLXB9. This gene plays a role in the development of the lower spine and bowel during embryonic growth, and its mutation disrupts these processes, leading to the syndrome’s characteristic malformations.
The condition typically follows an autosomal dominant inheritance pattern. This means that only one copy of the mutated MNX1 gene is sufficient to cause the syndrome. If a parent has Currarino syndrome, there is a 50% chance that each child they have will inherit the mutated gene and develop the condition. However, the severity of symptoms can vary widely among affected family members, a phenomenon known as variable expressivity.
While many cases are inherited, some individuals with Currarino syndrome have no family history of the condition. In these instances, the MNX1 gene mutation is believed to have occurred spontaneously. MNX1 mutations are identified in nearly all familial cases and in approximately 30% of sporadic cases.
Diagnosis Process
The diagnosis of Currarino syndrome often begins with a suspicion based on clinical symptoms, particularly severe, early-onset constipation that does not respond to conventional treatments. A physical examination, including a digital rectal examination, can also provide initial clues by revealing abnormalities in the anorectal region or suggesting a presacral mass.
Imaging techniques are subsequently used to confirm the physical components of the triad. Plain X-rays of the lower spine are performed to visualize the sacral anomaly, which may show the characteristic “scimitar sacrum” or other defects. A magnetic resonance imaging (MRI) scan of the pelvis is then typically conducted to provide detailed images of the sacrum, the spinal cord, and to clearly identify and characterize any presacral mass, such as a meningocele or teratoma. MRI is particularly effective at revealing the details of anorectal malformations and associated spinal issues, such as tethered cord syndrome.
A definitive diagnosis is often confirmed through genetic testing for MNX1 gene mutations. This testing identifies the specific genetic alteration responsible for the syndrome, aiding in diagnosis and genetic counseling. Genetic testing can detect the MNX1 mutation in about 57-65% of patients.
Management and Treatment Approaches
The management of Currarino syndrome focuses on addressing the specific malformations present and alleviating associated symptoms. Surgical intervention is often necessary, especially for the presacral mass. Surgical removal of the presacral mass is performed to prevent potential complications such as infection, particularly meningitis if the mass is a meningocele connected to the spinal canal, or to relieve pressure on surrounding organs like the rectum or bladder.
The surgical approach can vary depending on the type and location of the mass, sometimes involving a combined anterior and posterior procedure. For instance, an anterior sacral meningocele may be treated with transdural ligation of its neck, while solid tumors like teratomas require excision. Neurosurgeons and general surgeons often collaborate in these complex procedures to ensure comprehensive care.
Beyond surgery, long-term management of symptoms, especially chronic constipation, is a significant aspect of care. This involves a combination of dietary adjustments, the use of laxatives, and tailored bowel management programs. Other specialists, such as urologists, may also be involved if there are associated urinary tract issues.
Prognosis and Lifelong Care
With proper diagnosis and consistent medical management, the long-term prognosis for individuals with Currarino syndrome is generally favorable. While the condition involves congenital malformations, proactive treatment can significantly improve quality of life and prevent severe complications.
Lifelong follow-up with a multidisciplinary medical team is important to manage chronic symptoms, such as constipation, and to monitor for any potential long-term issues that may arise. Ongoing care ensures new or worsening symptoms are addressed promptly, allowing for treatment adjustments. Regular check-ups help optimize bowel and bladder function and monitor for rare complications like malignant transformation of presacral masses.