BACKGROUND: Hypersensitivity pneumonitis (HP) is an immune-mediated diffuse lung disease. Significant improvement in lung function and diffusing capacity after treatment was previously demonstrated, while long-term data focusing specifically on peripheral airway impairment and peak oxygen uptake (fitness) are lacking. Hence, the aim of this study was to conduct a comprehensive study to determine the stability of pulmonary function and fitness in patients previously diagnosed with HP.

METHODS: We performed a cross-sectional follow-up study with inclusion of longitudinal data if available in patients previously diagnosed with biopsy and high-resolution computed tomography-verified HP during childhood. We performed multiple breath wash-out (LCI2.5 ), spirometry (FEV1 ), bronchiodilator responsiveness test, diffusing capacity (DLCO and DLCO /VA ), body-plethysmography (TLC), and peak oxygen uptake (VO2peak ). St. George Respiratory Questionnaire was used as a measure of respiratory quality of life.

RESULTS: Twenty two patients were assessed. LCI2.5 was abnormal in 47.4% compared to abnormal FEV1 in only 9.1% and without significant bronchiodilator responsiveness. DLCO and TLC were abnormal in 40.9 and 13.6%, respectively, while DLCO /VA was within normal range. Only 11.1% demonstrated abnormal VO2peak . All longitudinally assessed outcomes remained unchanged between end of treatment and time of follow up.

CONCLUSIONS: A large proportion of patients previously diagnosed with HP had abnormal LCI2.5 in contrast to normal spirometry. Spirometric outcomes, TLC, and diffusing capacity were persistently slightly reduced, but stable, and VO2peak was excellent at time of follow-up. Long-term prognosis in children with HP appears favorable although persistent peripheral airway involvement of unknown clinical significance was demonstrated in almost half of the patients. Pediatr Pulmonol. 2016;51:830-837. © 2015 Wiley Periodicals, Inc.