Bronchoalveolar lavage fluid findings in children with hypersensitivity pneumonitis.

Bronchoalveolar lavage (BAL) has been shown to be useful in the diagnosis of hypersensitivity pneumonitis (HP) in adults, the typical constellation being lymphocytosis with a decrease in the CD4/CD8 ratio. Only limited data exist for the diagnostic value of BAL cytology in paediatric patients with this disorder. Children aged 6-15 yrs (n=9) with acute HP were studied. BAL was performed before initiation of anti-inflammatory treatment via a flexible bronchoscope in the middle lobe with 3 mL x kg body weight(-1) normal saline warmed to body temperature; BAL cytology and lymphocyte surface markers were compared with age-matched controls. The percentage of lymphocytes was significantly increased in all patients with HP. No significant differences were observed in the CD4/CD8 ratio between children without lung disease and those with HP. Increased expression of human leukocyte antigen-DR was found in seven of eight children with HP, whereas natural killer cells were elevated in five of eight children. Every patient had at least one of these two alterations in BAL fluid in addition to lymphocytosis. It was concluded that while lymphocytosis is generally present in children with hypersensitivity pneumonitis, the CD4/CD8 ratio is not increased in these patients. Assessing natural killer cells and human leukocyte antigen-DR expression appears to be a helpful adjunct in the diagnosis of paediatric patients with this disorder.