Final answer:
A vitamin D deficiency can cause Osteomalacia, an abnormal metabolic bone disease characterized by soft bones with a tendency to break easily.
Step-by-step explanation:
A vitamin D deficiency can cause Osteomalacia, which is an abnormal metabolic bone disease. Osteomalacia is characterized by soft bones with a tendency to break easily. Vitamin D is necessary for the absorption of calcium and phosphate, so a deficiency can lead to impaired bone formation and mineralization.