Effect of Oral Methyl Prednisolone on Different Radiological Patterns of Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP) is an immune-mediated disorder that causes inflammation of interstitial lung, bronchioles, and alveoli. Although corticosteroids have been used as first line treatment for HP for many years, it does not provide satisfactory results in all patients. The aim of this study is to compare the effect of oral methylprednisolone on different radiological patterns of HP to identify the most adequate candidates for corticosteroids.

Fifty-three patients with confirmed diagnosis of HP were divided into two groups according to their radiological patterns based on high resolution computed tomography (HRCT) findings. The first group included 21 patients with fibrotic HP (fHP), the second group included 32 patients without fibrosis; non-fibrotic HP patients (nfHP). The second group is divided into 3 subgroups: mosaic, attenuation, centrilobular nodules and finally, ground-glass opacities. All patients were administered methylprednisolone by dose 0.5mg/kg/day for eight consecutive weeks. HRCT was performed at the beginning of the study. Spirometry, six-minute walk and oximetry were performed periodically to assess the patients' progress.

Upon finalizing the treatment process, a significant improvement was noticed in FEV1 (p < 0.001), FVC (p <0.001), six-minute walk test (p =0.001) and oximetry (p <0.05) in nfHP compared to the fHP patients. However, there was a significant improvement in (p <0.01), FVC (p <0.01), oximetry (p <0.01) and six-minute walk test (p <0.01) in fibrotic patients after receiving the treatment. There was no significant difference in the response of FEV1 (p =0.82), FVC (p =0.15), six-minute walk test (p =0.36) and oximetry (p =0.27) among the subgroups of nfHP patients.

It was accordingly concluded that corticosteroid treatment is more effective in treatment of nfHP than fHP patients but still has effect on fibrotic patients. There is no significant difference in the response to corticosteroids among nfHP patients' subgroups.