Dental OSCE (Objective Structured Clinical Examination) Practice Exam

In a case where alkaline phosphatase is elevated and phosphorus is normal, which disease could be suspected?

1. Osteogenesis imperfecta

2. Paget's disease

3. Hyperparathyroidism

4. Osteoporosis

The correct answer is: Paget's disease

The presence of elevated alkaline phosphatase levels combined with normal phosphorus levels suggests an underlying condition characterized by increased bone turnover or abnormal bone metabolism. Paget's disease of bone is a specific condition associated with significantly elevated alkaline phosphatase due to increased osteoblastic activity as the bone remodels excessively. In Paget's disease, the bone undergoes a disorganized restructuring, leading to larger but weaker bone mass. The hallmark findings include the elevation of alkaline phosphatase levels, which reflects increased osteoblastic activity, while serum phosphorus generally remains normal unless there are complications or secondary effects from the disease. In contrast, conditions such as osteogenesis imperfecta and osteoporosis typically do not present with significantly elevated alkaline phosphatase, and hyperparathyroidism usually results in elevated calcium and phosphorus levels due to increased bone resorption. Thus, the combination of elevated alkaline phosphatase with normal phosphorus is particularly indicative of Paget's disease, making it the most likely diagnosis in this scenario.