What is typically found in bronchoalveolar lavage (BAL) in patients with hypersensitivity pneumonitis?

In patients with hypersensitivity pneumonitis, bronchoalveolar lavage (BAL) typically reveals marked lymphocytosis. This finding is characterized by an increased number of lymphocytes in the BAL fluid, which reflects the immune response to the inhaled antigens that trigger hypersensitivity pneumonitis.

The condition is associated with a T-cell mediated immune response, and the lymphocytic infiltration is indicative of the type of inflammation seen in this disease. The presence of lymphocytes can help differentiate hypersensitivity pneumonitis from other respiratory conditions that might show different cellular responses, such as asthma or infections.

In contrast, the other options do not align with the typical findings in BAL fluid for hypersensitivity pneumonitis. Eosinophilia, which involves an increase in eosinophils, is more commonly associated with allergic responses, while neutrophilia indicates an acute inflammatory response, typically seen in infections or acute lung injury. A normal BAL cell count would not be expected in a patient with hypersensitivity pneumonitis, as the disease is characterized by specific immune-mediated changes in the lung environment. Thus, marked BAL lymphocytosis is the hallmark finding indicative of this condition.