What symptom would likely be observed in a patient with serum sickness?

In serum sickness, nephritis is a common symptom due to the immune response triggered by the formation of immune complexes. These complexes can deposit in the kidneys, leading to inflammation and damage. This condition may manifest as glomerulonephritis, which is characterized by symptoms such as hematuria (blood in urine), proteinuria (excess protein in urine), and renal impairment.

The renal involvement is a direct consequence of the body's reaction to foreign proteins (typically from antiserum or other immunotherapies), resulting in an immune-mediated damage to kidney tissue. Recognizing nephritis as a symptom is crucial, as it highlights the systemic nature of serum sickness and its potential impact on organ systems.

Other symptoms in serum sickness might include fever, rash, joint pain, and lymphadenopathy, but nephritis stands out due to its clear association with the renal impairment that can occur in this condition.