An individual with hepatomegaly and jaundice has HBsAg positive, IgM anti-HBc positive, IgM anti-HAV negative, and anti-HCV negative. This serologic pattern supports which diagnosis?

• A. hepatitis A
• B. acute hepatitis B
• C. chronic hepatitis B
• D. hepatitis C

Answer: (C)

Key idea: IgM anti-HBc signals an acute hepatitis B infection. When someone has active HBV infection, HBsAg is present, and during the acute phase the body makes IgM anti-HBc. If the infection becomes chronic, IgG anti-HBc predominates and IgM anti-HBc is no longer present. The absence of IgM anti-HAV makes hepatitis A unlikely, and the absence of anti-HCV argues against hepatitis C. So this serologic pattern—HBsAg with IgM anti-HBc in the setting of acute liver symptoms—best fits acute hepatitis B rather than chronic HBV.