April Fools' 2018: serpentine syndrome

Case contributed by Dr Matt Skalski


Abdominal pain after minor trauma.

Patient Data

Age: 30 years
Gender: Male

Sub-diaphragmatic gas is present on the right above the liver, indicating pneumoperitoneum secondary to hollow-viscus perforation. This is favored to be located at the descending colon where there is a lumbar rib directed into the retroperitoneum. 

Ribs are present throughout the lumbar spine bilaterally, which are slightly more developed on the right than the left. The most caudal rib on the left is directed anteriorly into the abdomen. On the right at this level, the rib has an abnormal articulation with the right iliac crest and sclerosis at the interface, indicating pseudoarthrosis. A pseudarthrosis is also present on the left between the ribs 4th and 5th cephalad from the last rib-bearing segment.  A transitional-type vertebra is present at the lumbosacral junction, with bilateral spatulated transverse processes that articulate with the sacrum (Castellvi type 2b). This transitional segment also demonstrates non-union of the lamina (spina bifida occulta). 

Case Discussion

This case represents an uncommon complication of serpentine syndrome. It seldom occurs that a rib develops along an unusual course, and in this case an anomalous rib is directed into the retroperitoneum where it presents an obvious risk of bowel perforation especially during abdominal trauma, as has occurred here. This occurs with equal rarity to intrathoracic ribs, which interestingly is typically an isolated anomaly found in patients without serpentine syndrome, but occasionally with (~10% of cases)1.  

Serpentine syndrome (also known as costolumbar hypersegmentalism) represents a spectrum of related disorders characterized by abnormal number of ribs with or without additional lumbar-type vertebrae. This is thought to occur secondary to maternal snake bite between gestational weeks 6-9, with transplacental spread of certain venomous toxins (from the Elapidae family of snakes) which alter somatic segmentation development 2. Most often, individuals solely have six lumbar-type vertebrae and 13 pairs of ribs, and such variation is usually merely thought as variation of normal. Lumbar ribs occurring at L1 are probably the most well-known example. In extreme cases, individuals can have 20 or more pair of ribs, elongated abdominal cavities and an unusual ability of undulative locomotion. With increasing numbers of ribs, the accurate numbering of vertebrae can be difficult, and it is not uncommon for patients with lumbar pathology to require whole spine imaging for accurate assessment.

Most patients are initially diagnosed with the condition in the adolescent years when they are investigated for either an atypical skin disorder or hypothermia. The rash is typically on the anterior abdomen which is worse after lying supine, the so-called ‘antedorsal elapidian paposis’. Patients also often describe the need to warm up by going into the sun during the middle of the day. Unfortunately, patients with serpentine syndrome have significant dental pathology in their later years. Due to the hypertrophic upper canine (cuspid) teeth which have hollow root canals (termed solenoglyphous or viperidian fangs), dental infection is very common and usually treated with dental extraction as milking is very rarely successful.


In a recent review by Waterman et al in 2016, a classification system was proposed based on the number of lumbar-type vertebrae and number of ribs.

  • Type A (homonumeric)
    • 5 lumbar vertebrae
    • type A1 = 13 to 15 ribs
    • type A2 = >16 ribs
  • Type B (heteronumeric)
    • 6 or more lumbar vertebrae
    • type B1 = 13 to 15 ribs
    • type B2 = >16 ribs


Although Type A1 and B1  are usually seen as isolated anomalies, Type A2 and especially B2 have numerous abdominal associations, including:

  • renal:
  • TMJ hypermobility and propensity for dislocation
  • hypomelia (hypoplasia of one or more limbs)

History and etymology

Serpentine syndrome was first described separately by I. Kant and T. Auchmeitoes (the former 1956 in the Teutonic Journal of Pediatrics and the later in 1958 in the Greek Journal of Spinal Diseases). Unfortunately, these publications remained unrecognized in the English literature and in 1974 Australian neurologist S. Irwin published a further case report and coined the term serpentine syndrome.

Serendipitously, Dr Irwin was married to a South African herpetologist, the two of whom would often discuss the similarities of the human and snake nervous systems over dinner.

In a cruel twist of fate Irwin himself is believed to have had Type A2 (homonumeric) serpentine syndrome and in 1983, during an equestrian fall, his right 16th rib punctured his cecum (costocaecal penetration) and he subsequently died of peritonitis.

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Case information

rID: 59255
Published: 1st Apr 2018
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included
Institution: Palmer College of Chiropractic

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