What is Metabolic Bone Disease?

This Bearded Dragon can tell you that he’s much better without it!

By Jeffrey Fowler, DVM

Scientifically called nutritional secondary hypoparathyroidism, Metabolic Bone Disease (MBD) can affect many types of animals. It involves a dietary lack of calcium and often vitamin D3, which aids in the absorption of calcium from the intestinal tract. It rarely, but sometimes includes an imbalance of too much phosphorous. This form comes typically from advanced renal failure, secondary renal hypoparathyroidism.

Dr. Fowler recently saw Kai, a bearded dragon, who was suffering from MBD. When Kai came to PPVC, he was a bit lethargic and very weak. His foreleg was bent at an unusual angle, he was very thin, and his spine was still straight, but he showed little muscle mass. Though kai was tiny, about 16 grams,  we were able to take x-rays using our dental x-ray machine. In the picture below, you can see how his bones were soft and bending, meaning he was not getting enough calcium. Read on for more about Kai’s story and MBD in general.

In many species, the body creates Vitamin D3 when ultraviolet B light (UVB) hits the skin. UVB, a short wavelength high frequency form of light, is invisible to the human eye. Some animals do get D3 from their diet alone. When animals do not have enough calcium or D3 we see fibrous osteodystrophy. This is the softening of hard bone as well as replacement by fibrous connective tissue resulting in deformed swelling of long bones, skull and jaws. With treatment proper hardness can be restored, however deformities are often permanent. As long as they haven’t progressed too far, once they have been stabilized, your reptile should be able to live a normal active life even if its bones are slightly bent.

In the human species, we are more familiar with calling this disease Rickets. In horses, it is called “big head;” in dogs and cats, we use the term “rubber jaw” though it is rare and mostly seen in poorly cared for puppies and kittens. Birds can also get MBD.

In reptiles, MBD is principally a disease of improper nutrition and care. It typically occurs in younger, growing, sun-loving reptiles like bearded dragons, green iguanas, and turtles, though it can be seen in other reptile species as well. We diagnose MBD based on the history of the problem: How is the habitat set up? What kind of lighting is used? What diet and supplements does the reptile eat? Then we rely on clinical signs in the patient. As you might imagine, reptiles in a home environment may not get everything they would get in a natural environment.

Two forms of MBD exist. If a beardie is very weak, does not defecate, has difficulty moving, its eyelids are droopy and/or has tremors in its toes, these are signs our PPVC vets look for because it means blood calcium levels are too low for muscle contraction. In the second form, they develop swollen leg bones, often bent, a twisted spine, and a rubbery jaw. In turtles, shells become very soft. Often, we see a mix of both forms.

The pictures below show Kai when he first came to us, pliable in mind and body. With his folks’ help, including better UVB lighting in his environment and calcium supplementation as well as feeding him live bugs (gut loading) for better nutritional value, we were together able to restore him to the beautiful happy lizard you see at the top of this blog post. We all couldn’t be happier that Kai is thriving in his environment!

So how do you treat MBD?

First and foremost, dietary corrections are needed, including gut loading the prey and possibly dusting the prey with calcium (without added D3 in most cases). Then, adding or upgrading UVB light in the habitat so they can produce enough D3 to absorb that calcium correctly is important. In severe cases, our patient must be tube fed with additional calcium. We make sure it gets into the body cavity by mixing it with fluids and sometimes even administer it intravenously. In those with poor contraction and twitching, IV therapy can cause a dramatic improvement.

Once your scaly baby is on the road to recovery, we follow up with the basic care to make sure everything is properly set up for your reptile to continue to live a healthy, happy life. As always, if you need anything or have questions, don’t hesitate to call us at 719-475-1747!