Metabolic bone disease (MBD), or nutritional secondary hyperparathyroidism, is a complex disease and is probably the most common health problem of pet bearded dragons. It is most often seen in juvenile bearded dragons (less than 2 years old).

 

MBD is generally caused by feeding an improper diet that is high in phosphorus and low in calcium or Vitamin D3 (caused either by a direct nutritional deficiency of vitamin D3 or a lack of exposure to UV-B light required for lizards to make vitamin D in their skin).

 

Common signs include swelling of the lower jaw, softening of the jaw and facial bones ('rubber jaw'), and/or swelling of the hind limbs (fibrous osteodystrophy). Legs also commonly tremor as the animal tries to walk, and many bearded dragons with MBD are so weak that they can neither walk nor push their bodies up in a normal stance, but instead crouch low to the ground or lay on their abdomens. X-rays reveal thin bone tissue (decreased density), widening and thickening bone shafts, and possibly fractures that appear to have occurred in the absence of any trauma or for no apparent reason.  Greenstick fractures (bones that appear to fold or bend rather than break apart) may also occur when bones are soft. Blood tests may show a low calcium level and an imbalance of calcium and phosphorus, with phosphorus being higher than calcium, instead of in the 2:1 calcium to phosphorus ratio desirable in reptiles.

 

As the condition progresses, muscle twitching, seizures, loss of appetite, and loss of energy (lethargy) are seen.