Congenital Anomalies and Embryonic Development of Caudal Appendages

The formation of caudal appendages in the human embryo originates from the tail bud, a specialised cell population at the posterior primitive streak. Precise regulation of signalling pathways—most notably Wnt, FGF and retinoic acid—is required for the differentiation of mesodermal and ectodermal derivatives in the developing tail region. Somite segmentation and vertebral patterning are controlled by Hox gene expression, ensuring the proper formation of the sacrococcygeal spine and associated soft tissues. In normal human development the visible tail regresses by apoptosis and remodelling of the caudal eminence. When these processes are disrupted, a spectrum of congenital anomalies may emerge. True tails represent persistence of embryonic tissue containing adipose, connective and occasionally muscular elements without vertebral involvement. Pseudotails appear as prominent masses but are often composed of fat or cartilage and may signal underlying spinal dysraphism. More complex malformations include polymelia or accessory perineal structures, which can involve ectopic limbs or scrotal tissue due to aberrant germ layer differentiation. Recognition of these variants has implications for prenatal screening, early diagnosis and surgical planning, as some lesions conceal occult neural tube defects or tethered spinal cords. Advances in prenatal imaging and molecular genetics are illuminating the pathogenesis of tail‐region anomalies and guiding targeted intervention to preserve neurological function and optimise urogenital and orthopaedic outcomes.

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Congenital Anomalies and Embryonic Development of Caudal Appendages publication trend

The graph below shows the total number of articles in congenital anomalies and embryonic development of caudal appendages across all publications each year (not limited to Nature Index journals).

Technical terms

Tail bud: Posterior group of undifferentiated cells at the primitive streak that gives rise to the caudal eminence and associated structures.

Spinal dysraphism: A spectrum of neural tube closure defects affecting the vertebral arches, meninges and spinal cord.

True tail: Persistent embryonic caudal remnant containing adipose and connective tissue without vertebral elements.

Pseudotail: Caudal appendage that mimics a tail but comprises fatty or cartilaginous tissue and may indicate underlying dysraphism.

Neurogenic bladder: Bladder dysfunction resulting from disrupted neural control, often associated with spinal cord anomalies.

References

1. A True Human Tail In A Neonate Born In Saudi Arabia: A Case Report. Cureus (2024).
2. A case of dumbbell-shaped accessory scrotum with concomitant lipoma. Surgical Case Reports (2024).
3. Pseudotail with closed neural tube defect and neurogenic bladder masquerading as posterior urethral valve: a case report. Annals of Pediatric Surgery (2021).