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Multiple synostoses syndrome

Case contributed by Kylie Lopes Floro
Diagnosis almost certain


Child presenting with hallux varus. Congenital fusions?

Patient Data

Age: <15years
Gender: Unknown
  • complete bony coalition of the talus and navicular bilaterally
  • near complete coalition between the lateral cuneiform and cuboid bone bilaterally.  
  • small 6 x 8 mm rounded ossicle projected distal and medial to left navicular in keeping with a separate accessory navicular (os tibiale externum)
  • mild right hallux valgus
    • 20º angulation of the right 1st proximal phalanx relative to 1st metatarsal
    • slight lateral subluxation of the articular surface of the proximal phalanx relative to head of 1st metatarsal
    • right 1st  to 2nd intermetatarsal angle is borderline measuring 9º (increased relative to the contralateral right foot 5º)
  • 1st metatarsals bilaterally are relatively short
  • bilateral biphalangeal 3rd, 4th and 5th toes (biphalangeal toes can be seen as a normal variant)
  • bilateral pes planus

  • bilateral 3rd, 4th and 5th digital proximal symphalangism
  • 1st metacarpals bilaterally are relatively short
  • angulation of the distal 5th interphalangeal joints

Case Discussion

Multiple synostoses syndrome (SYNS) is an autosomal dominant condition with variable penetrance. It is characterized by ankylosis of the PIP joints, carpal and tarsal bone, vertebrae (at various levels), brachydactyly, nail hypoplasia, humeral-radial synostoses, elbow semidislocation or cubital valgus, characteristic facial features (long face, broad tubular or a hemicylindrical nose, short philtrum, thin upper vermilion) and conductive hearing loss. There are four subtypes (see the related article for a description of each one of these).

As SYNS involves multiple joints fastidious analysis is required to determine the patient's subtype. Unfortunately, no further clinical details are available for this patient. Particular features which would further define this patients subtype include vertebral fusions (including level), facial anomalies, and a personal or family history of hearing loss.

This additional information is of particular importance as these subtypes align with specific genetic anomalies in genes which include NOGGIN, GDF5, GDF6 and FGF9 (see related article). These genes encode the protein which directly involves or interacts with the BMP signaling.

Case contributed by Kylie Lopes Floro and David Preston.

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