A 55-year-old man with bone pain and signs suggesting a bone-related disorder has a markedly increased alkaline phosphatase with a normal gamma-glutamyltransferase. Which diagnosis is most likely?

A 55-year-old man with bone pain and signs suggesting a bone-related disorder has a markedly increased alkaline phosphatase with a normal gamma-glutamyltransferase. Which diagnosis is most likely?

• A. Biliary obstruction
• B. Cirrhosis
• C. Hepatitis
• D. Osteitis deformans

Answer: (D)

When alkaline phosphatase (ALP) is markedly elevated but gamma-glutamyl transferase (GGT) is normal, the ALP is coming from bone rather than liver. ALP is produced by osteoblasts during bone formation, so conditions with increased bone turnover—like Paget disease of bone (osteitis deformans)—cause a prominent rise in ALP. GGT, on the other hand, is more specific to the liver and biliary tract; liver diseases such as biliary obstruction, cirrhosis, or hepatitis typically raise both ALP and GGT. In this scenario, the combination of bone-related symptoms and a high ALP with a normal GGT points most strongly to Paget disease of bone.

When alkaline phosphatase (ALP) is markedly elevated but gamma-glutamyl transferase (GGT) is normal, the ALP is coming from bone rather than liver. ALP is produced by osteoblasts during bone formation, so conditions with increased bone turnover—like Paget disease of bone (osteitis deformans)—cause a prominent rise in ALP. GGT, on the other hand, is more specific to the liver and biliary tract; liver diseases such as biliary obstruction, cirrhosis, or hepatitis typically raise both ALP and GGT. In this scenario, the combination of bone-related symptoms and a high ALP with a normal GGT points most strongly to Paget disease of bone.