Abstract
BACKGROUND: A conjoined parasitic twin is a grossly defective fetus or fetal parts attached externally to a relatively normal twin. Rachipagus conjoined twins are fused at the spine. Conjoined twinning is an exceedingly uncommon congenital abnormality, with rachipagus twinning being the rarest variant. OBSERVATIONS: The authors report the case of a rare parasitic rachipagus conjoined twin who was surgically managed at 9 weeks of age. The patient presented with skin-covered swelling on her upper back that resembled digits. Further study with computed tomography showed parasitic content of the digits and embryonic tissue and the absence of posterior elements of the T4 and T5 vertebrae without meningocele at the autosite. The patient underwent successful excision of the parasitic twin and subsequently had normal growth and development. LESSONS: Neural tube defects of varying degrees occur in almost all rachipagus parasites, which should be taken into account in the comprehensive treatment of the pathology. Patients vary in the degree of fusion, and preoperative imaging to demonstrate the complex surgical anatomy at the fusion site should be an integral part of treatment. A multidisciplinary team consisting of neurosurgeons, pediatric surgeons, and plastic surgeons is required. https://thejns.org/doi/10.3171/CASE24698.