There is an array of clinical signs of MBD. In young animals, an early sign, especially in green iguanas, is the inability to lift the trunk normally. This may be partial or complete. Normal iguanas will lift their body and tail closest to the body up off the ground while walking on any surface. Often, in early MBD, the iguana will lift the front half of the body up while walking, while dragging the pelvis and tail on the ground. In advanced cases, the iguana will drag itself along, unable to lift off the ground at all. This will progress to the complete inability to move in a forward motion, in spite of frantic fore and hind limb movements.
The mandible may become rubbery, and the maxilla may become soft, as well. Eventually, the lower jaw will retract, so that an underbite develops. This may be made even more evident by fibrous osteodystrophy of the jaw. It becomes difficult for a reptile to eat normally when the jaw is misshapen, so weight loss may be a sign of MBD.
A reptile or amphibian with MBD is often lame or reluctant to move. They are often weak. Since weakened bones are prone to fracturing, spontaneous fractures may occur, or fractures may occur from normal activity or handling. Deformities of the spine commonly occur. The rear limbs may become very weak or even paralyzed. If this occurs, the chance for recovery is poor, as this often interferes with urination and defecation.
Chelonians (turtles and tortoises) with early onset MBD often develop abnormal shells. Normally hard-shelled turtles and tortoises may have soft shells and the carapace may curve upwards along the edges. The skull often develops abnormally, and the chelonian often has an overgrown maxilla, resulting in the appearance of a parrot beak. Normally, turtles and tortoises lift their body up off the ground while walking, and with MBD, they may not be able to do so. Examination of the plastron may show signs of being dragged.
Adult reptiles and amphibians that develop MBD will not show the same problems as juveniles. Since they are not rapidly growing, bone and developmental problems do not occur. Usually, a lizard with adult-onset MBD presents with nervous system problems. Subtle signs, such as occasional twitching of toes, a limb or tail are the first signs. As problems with low calcium in the bloodstream (hypocalcemia) progress, twitching and muscle tremors become more evident, especially after exercise, such as swimming or walking. Tremors of the muscles become more severe and frequent. Without proper diagnosis and treatment, the muscle tremors can progress to seizures or tetany (prolonged seizure activity and twitching). Eventually, the herp will become very weak and the muscles will become flaccid. While this can occur in adult iguanas commonly, chelonians rarely, if ever, show signs of adult MBD.
The diagnosis of MBD, either in an adult or juvenile, may often be presumed based on the history (diet, husbandry, etc.) and physical examination. Radiographs may be helpful in determining the bone density (an indication of the amount of calcium present in the bone), any skeletal abnormalities (including irregularities of the skeletal system, fractures, etc.) and they may be useful in follow-up evaluation of treatment. However, rads are not essential for diagnosis of MBD in the juvenile form.
Blood tests may show low blood calcium and an elevation of the phosphorus level. With hypocalcemic adult MBD, the calcium level may be in the normal range, unless the blood is drawn during or immediately after a seizure or twitching episode. An inverse ca: phos ratio of the blood is strong evidence of MBD. Juveniles with MBD often have a low calcium level and an elevated phosphorus level, however some young herps with MBD may show levels within the normal range.
