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caudal dysplasia


Monday 5 April 2004

Definition: Caudal regression syndrome (CDS), or caudal dysplasia, is a congenital malformation characterized by various degrees of developmental failure involving legs, lumbar, sacral and coccygeal vertebra, and corresponding segments of spinal cord due to defect in neuralisation. This results in motor and sensory deficits.

Other congenital anomalies such as gastrointestinal, genito-urinary or congenital heart disease may be present.

Some authors consider sirenomelia to be an extreme form of caudal regression syndrome (CRS), but they can be two distinct entities. Maternal diabetes mellitus is considered to be an important predisposing factor for both caudal regression syndrome and sirenomelia.


- lumbar agenesis
- sacral agenesis
- coccygeal agenesis


The exact etiology of this syndrome is unclear and maternal diabetes, genetic factors, teratogens and vascular anomalies altering blood flow have been hypothesized to play a role in its pathogenesis.

- dysembryoplasic origin

  • The embryological origin is believed to be a failure of formation of the most distal part of the notochord that will then influence on one side the development of neural and vertebral structure of the lower spine and on the other the development of the cloacal-derived structures.

- vascular origin

  • anomaly of the unpaired vessels originating from the aorta, a likely relict of a persisting vitelline artery (16801960)


- overall incidence: 1 in 7,500 live births
- maternal diabetes in about 16% of cases (relative risk for a child of a diabetic mother: about 1%)


- vertebral anomalies

  • partial or total unilateral sacral agenesis
  • sacral agenesis
  • sacral hypolasia
  • total agenesis of the lumbar and sacral spine (absence of vertebrae above T10 is incompatible with life)

- spinal cord anomalies (2028749)

  • sacral hypoplasia
  • minor fusion of sacral roots
  • low-positioned conus medullaris
  • fusion of the sacral roots and ganglia
  • spinal ganglion cell heterotopias
  • filar lipoma
  • absence of the last sacral roots and ganglia
  • additional tethering of the spinal cord
  • total lack of the lumbosacral spinal cord
  • dysplasia of the T11 and T12 cord segments

- neural tube defects

- anorectal anomalies

  • anal atresia (imperforate anus)
    • complete covered anus
  • anorectal atresia
  • rectovaginal fistula

- genital malformations

  • malformed external genitalia

- hydrocephalus
- dermoid cysts

- urinary malformations

  • exstrophy of the urinary bladder

- renal malformations

  • bilateral renal agenesis
  • horseshoe kidney
  • solitary kidney

- incomplete development of the pelvis
- lower limbs anomalies

  • absent fibula
  • short femora
  • sirenomelia (fusion of the lower extremities)
    • fused femurs or common femur
    • fused tibias or common tibia without fibula
    • rudimentary unique foot


- skeletal anomalies

- situs inversus (1267298, 8719727)
- cardiovascular anomalies
- tracheoesophageal fistula

Classification (Renshaw, 1978)

- Type I: total or partial unilateral sacral agenesis.
- Type II: variable lumbar and total sacral agenesis with the ilia articulating with the sides of the lowest vertebra.
- Type III: variable lumbar and a total sacral agenesis, the caudal end-plate of the lowest vertebra resting above either fused ilia or an iliac amphiarthrosis
- Type IV : with increasing severity, soft tissues of both the lower limbs are fused. They have two femora and two tibiae with a single central fibula between the two tibiae.
- Type V : is also known as "sirenomelia" or "mermaid syndrome" wherein there is a single femur and tibia.

Classification of caudal dysgenesis

- 1) caudal dysgenesis with complete absence of the sacrum and lower vertebrae, multiple congenital anomalies, and association with maternal diabetes

- 2) agenesis of the distal sacral or coccygeal segments

- 3) hemisacral dysgenesis with presacral teratoma

- 4) hemisacral dysgenesis with anterior meningocele (SDAM) (MIM.600145)


- mutations in the HLXB9 gene, a member of the HLXBs gene family in type IV form of caudal regression syndrome (CRS) characterized by hemisacrum
- maternal diabetes
- maternal prediabetes

Differential diagnosis

- familial sacral dysgenesis

  • familial hemisacrum

See also

- anorectal malformations
- sirenomelia

Case records

- Case #10038: Caudal dysplasia
- Case #13394: Caudal dysplasia in maternal diabetes


- Padmanabhan R, Naruse I, Shiota K. Caudal dysgenesis in staged human embryos: Carnegie stages 16-23. Am J Med Genet. 1999 Nov 19;87(2):115-27. PMID: 10533025

- Welch, J. P.; Aterman, K. : The syndrome of caudal dysplasia: a review, including etiologic considerations and evidence of heterogeneity. Pediat. Path. 2: 313-327, 1984.