When alkaline phosphatase is markedly elevated with a normal gamma-glutamyltransferase, the source is most likely bone rather than liver. Which condition fits this pattern?

When alkaline phosphatase is markedly elevated with a normal gamma-glutamyltransferase, the source is most likely bone rather than liver. Which condition fits this pattern?

• A. Biliary obstruction
• B. Cirrhosis
• C. Osteitis deformans
• D. Acute pancreatitis

Answer: (C)

When alkaline phosphatase is markedly elevated but gamma-glutamyltransferase remains normal, the enzyme source is usually bone rather than liver. Gamma-GT is a marker of hepatic/biliary origin, so elevated GGT alongside ALP points to a liver source; a normal GGT with high ALP points to a bone source and bone-related disease. Osteitis deformans, also known as Paget disease of bone, involves increased bone turnover with prominent osteoblastic activity. This drives a substantial rise in alkaline phosphatase from bone, while GGT stays normal because the liver isn’t the source. Biliary obstruction or cirrhosis would typically raise ALP and GGT together, reflecting hepatic involvement, and acute pancreatitis doesn’t produce the classic bone-dominant ALP elevation pattern. Thus, the pattern most consistent with the question is osteitis deformans.

When alkaline phosphatase is markedly elevated but gamma-glutamyltransferase remains normal, the enzyme source is usually bone rather than liver. Gamma-GT is a marker of hepatic/biliary origin, so elevated GGT alongside ALP points to a liver source; a normal GGT with high ALP points to a bone source and bone-related disease.

Osteitis deformans, also known as Paget disease of bone, involves increased bone turnover with prominent osteoblastic activity. This drives a substantial rise in alkaline phosphatase from bone, while GGT stays normal because the liver isn’t the source. Biliary obstruction or cirrhosis would typically raise ALP and GGT together, reflecting hepatic involvement, and acute pancreatitis doesn’t produce the classic bone-dominant ALP elevation pattern.

Thus, the pattern most consistent with the question is osteitis deformans.