Histopathological findings in patients with refractory nonfibrotic hypersensitivity pneumonitis

Background The course of hypersensitivity pneumonitis (HP) is characterized by variable patterns of disease progression. Refractory HP is defined as poor or lack of response to different modalities of treatment with worsening of the functional status. Aim To assess the causes of refractory HP and to evaluate the correlation between disease progression and different histopathologic findings in patients with HP. Patients and methods We included 20 patients who were diagnosed primarily as HP and proved to be refractory to treatment. All patients were subjected to the following: complete history taking and clinical examination, spirometry, 6-min walk test, high-resolution CT chest, echocardiography, and transbronchial lung biopsy. Results Female sex was predominant among the studied patients. The mean age of our patients was 39.9±13.49 years. Overall, 65% of these patients were raising birds, but the offending agent was not identified in 30% of patients. Almost all patients presented with restrictive lung functions (mean forced vital capacity=59±10%), and radiologically, they mainly presented with centrilobular ground-glass and nodular opacities. Histopathological results showed that there was isolated HP pathology in 40% of patients and HP with associated pathologies in 60% of cases without significant fibrotic changes. Conclusion HP is more common in women and middle ages. Histopathological findings revealed no significant fibrotic changes in most of the cases, so other mechanisms may be involved in disease progression and may affect treatment response.