Which of the following is a clinical feature of hepatitis B but not hepatitis A?

The presence of chronic infection is a distinctive clinical feature of hepatitis B that does not typically occur with hepatitis A. Hepatitis B can lead to a long-term, chronic infection in some individuals, particularly when the virus is contracted at birth or in early childhood. This chronic infection can result in ongoing liver damage, cirrhosis, and an increased risk of liver cancer over time.

In contrast, hepatitis A is generally an acute viral infection that does not lead to chronic disease. Once individuals recover from hepatitis A, they typically develop lifelong immunity to the virus without any progression to a chronic state.

The other options listed can occur in both types of hepatitis. For example, fulminant hepatitis can occur in severe cases of either infection, jaundice is a common symptom in both hepatitis A and B, and dark urine may also be seen in both conditions as a result of excess bilirubin in the blood. However, the hallmark of chronic infection sets hepatitis B apart significantly in terms of its clinical implications.