A 14-year-old girl presents with facial puffiness, fatigue, and decreased appetite. She is HBsAg and HBeAg positive. What is the likely diagnosis?

The clinical presentation of the 14-year-old girl suggests that she is experiencing symptoms consistent with a renal condition, and the positive HBsAg and HBeAg indicate active hepatitis B infection. Membranous nephropathy is known to be associated with viral infections, particularly hepatitis B. The presence of facial puffiness, fatigue, and decreased appetite aligns with nephrotic syndrome, where there's often significant kidney damage causing proteinuria.

Membranous nephropathy specifically can result from the deposition of immune complexes in the glomeruli, and these immune complexes can be triggered by viral infections, including hepatitis B. In adolescents and young adults, hepatitis B is a well-known cause of secondary membranous nephropathy.

While nephrotic syndrome encompasses various conditions characterized by substantial proteinuria, it is often a broader term and could encompass different underlying causes. In this case, the direct association with hepatitis B and the clinical features align more specifically with membranous nephropathy as the likely diagnosis rather than minimal change disease or acute glomerulonephritis, which have different implications and associations.