During a routine check up, a 67-year-old man is found to have a level of serum alkaline phosphatase three times the upper limit of normal. Serum calcium and phosphorus concentrations and liver function test results are normal. He is asymptomatic. The most likely diagnosis is :
Answer is C (Paget's disease of bone) : Elevated alkaline phosphatase with normal serum Ca2+ and PO4 is characteristic of Paget's disease. `Serum calcium and phosphorus levels are normal in paget's disease. Discovery of hypercalcemia even in presence of immobilization should prompt a search for another cause of hypercalcemia' - Harrisons `Serum Alkaline phosphatase levels are markedly elevated reflecting the marked osteoblastic activity '-Chandrasoma Taylor Paget's disease of bone is characterized by the following pathological process: Over activity of osteoclasts causing widespread bone resorption (principal abnormality in Paget's disease) Compensatory increase in osteoblastic new bone formation (Marked elevation of Alkaline phosphatase levels) Total bone volume may be maintained but the pagetic bone can be recognized as it is structurally disorganized and more susceptible to deformities and fractures. Condition Serum Ca Serum phosphorus Alkaline phosphatase PTH Paget's disease N N Increase N
Metastatic bone disease
Primary hyperparathyroidism
Paget's disease of bone
Osteomalacia