Thrombocytopenia-Absent Radius (TAR) Syndrome with VACTERL Association
The clinical triad of absent radius, solitary kidney, and scoliosis in a child most strongly suggests VACTERL association (Vertebral, Anorectal, Cardiac, Tracheoesophageal, Renal, Limb anomalies), though Thrombocytopenia-Absent Radius (TAR) syndrome should also be considered if thrombocytopenia is present. 1, 2
Diagnostic Evaluation
Initial Imaging and Laboratory Assessment
Obtain complete spine radiography (PA and lateral views) to characterize the scoliotic deformity, assess severity using Cobb angle measurement, and identify any congenital vertebral anomalies such as hemivertebrae, butterfly vertebrae, or segmentation failures 3
Perform MRI of the complete spine immediately as intraspinal anomalies occur in 43% of congenital scoliosis patients, including syrinx (most common), tethered cord, diastematomyelia, and Chiari malformation 3, 2
- This is mandatory before any surgical planning, as neurologic examination alone has only 62% accuracy for detecting intraspinal anomalies 3
Order echocardiography urgently as cardiac anomalies are the most common associated defect, occurring in 54% of congenital scoliosis patients, with ventricular septal defect being most prevalent 2
Confirm renal anatomy with ultrasound and radionuclide studies to document solitary kidney function and screen for additional urological anomalies, which occur in 37-39% of cases 2, 4
Obtain complete blood count with differential to evaluate for thrombocytopenia (suggesting TAR syndrome) and monitor platelet counts over time 3
Comprehensive Multi-System Screening
Perform voiding cystourethrogram to evaluate for vesicoureteral reflux and other urological anomalies, as 37% of congenital scoliosis patients have urological defects 2, 4
Screen for gastrointestinal anomalies including tracheoesophageal fistula, anorectal malformations, and intestinal atresia, which occur in 8-12% of patients with vertebral anomalies 1, 2
Evaluate for additional skeletal anomalies including clubfoot, polydactyly, and cervical spine instability with flexion-extension radiographs around age 4 years 3
Consider genetic testing including chromosomal microarray or exome sequencing if syndromic features suggest 22q11.2 deletion syndrome or other genetic conditions 3
Risk Stratification
High-Risk Features Requiring Urgent Intervention
The presence of hemivertebra with concurrent anomalies carries the highest risk, as 63.2% of hemivertebra patients have additional congenital anomalies, and 31.3% meet criteria for VACTERL association (≥3 organ system defects) 1
Unilateral bar with contralateral hemivertebra indicates aggressive curve progression exceeding 10° per year, requiring early surgical consultation 3
Diastematomyelia carries 70.1% risk of additional anomalies and requires immediate neurosurgical evaluation 1
Cardiac defects must be characterized fully before any anesthesia or surgical intervention, as they occur at twice the previously reported rate 2
Management Algorithm
Scoliosis-Specific Treatment
For curves <25° with low progression risk: Clinical examination and radiography every 6 months, limiting radiation exposure 3, 5
For curves 25-45° in skeletally immature patients: Bracing is indicated to prevent progression to surgical thresholds 5, 6
For curves >50° or rapidly progressive curves: Surgical consultation is mandatory, with preoperative MRI already completed per initial workup 5, 6
- CT with 3-D reconstruction may be added for presurgical planning to reduce instrumentation complications from 15.3% to 6.5% 3
Renal Management
Establish nephrology follow-up immediately as children with solitary functioning kidney are at significant risk for CKD progression due to glomerular hyperfiltration in reduced nephron mass 7
Monitor renal function with serum creatinine, blood pressure, and urinalysis at least annually, with more frequent monitoring if proteinuria or hypertension develops 7
Counsel families on renal protective measures including avoiding nephrotoxic medications, maintaining adequate hydration, and preventing urinary tract infections 7
Cardiac Management
Coordinate with pediatric cardiology for risk stratification and timing of any surgical interventions, as cardiac anomalies may contraindicate or delay orthopedic procedures 2
Obtain EKG screening if antiepileptic medications, hypocalcemia, or thyroid disease are present 3
Multidisciplinary Coordination
Establish care with a clinician experienced in VACTERL association or complex congenital anomalies for longitudinal coordination 3
Screen for feeding difficulties, gastroesophageal reflux, and constipation which commonly complicate multi-system anomalies 3
Evaluate hearing with audiogram and tympanometry as otologic anomalies may be present 3
Assess for developmental delays and provide early intervention services (physical, occupational, speech therapy) as needed 3
Critical Pitfalls to Avoid
Never assume isolated scoliosis when limb and renal anomalies are present—84% of congenital scoliosis patients have at least one additional organ defect, and 18% have ≥4 organ defects 2
Do not delay MRI evaluation as intraspinal anomalies occur in >20% of severe curves and alter surgical planning significantly 3, 6
Avoid overlooking the 12% incidence of the complete triad (spinal, cardiac, and urogenital defects), which requires comprehensive preoperative evaluation 2
Do not perform surgery without complete cardiac evaluation as perioperative complications can be devastating if cardiac defects are undetected 1, 2
Never assume normal neurologic examination excludes intraspinal pathology as physical examination has only 62% accuracy for detecting these anomalies 3