MBD is one of the most common and preventable health problems in captive reptiles. Without adequate UVB lighting, reptiles cannot synthesize vitamin D3 in their skin, which is essential for absorbing dietary calcium. The body then pulls calcium from bones to maintain blood levels, leading to soft, rubbery bones and jaw deformities. Early signs include lethargy, reluctance to move, trembling limbs, and swollen joints. Advanced cases show visible spinal kinks and jaw softening. Prevention requires proper UVB lighting replaced on schedule (output declines before bulbs burn out), calcium supplementation dusted on food, and a balanced diet. Early-stage MBD can often be reversed with corrected husbandry, but severe skeletal damage may be permanent.