Addition of Rituximab to Oral Corticosteroids in the Treatment of Chronic Hypersensitivity Pneumonitis

Updates in Hypersensitivity Pneumonitis: A Narrative Review

Purpose of Review

Hypersensitivity pneumonitis (HP) is an immune-mediated disease triggered by a known or unknown antigen. While reversible in the early stages of disease, progression toward irreversible pulmonary fibrosis may occur. This narrative review summarizes recent publications highlighting a methodical approach toward the diagnosis, classification, and management of fibrotic and nonfibrotic HP.

Recent Findings

Establishing the diagnosis of HP is often challenging given its variable clinical course, extensive inciting agents, and overlapping features with other interstitial lung diseases. Recently, HP has been re-classified into nonfibrotic and fibrotic subtypes based on radiographic and histopathological features. Chronic fibrotic HP is associated with significant functional impairment and increased mortality. In addition to antigen avoidance, immunosuppression is the cornerstone of management in nonfibrotic HP. Antifibrotic agents have emerged as a therapeutic option in halting the progression of chronic fibrotic HP.

Summary

The combination of clinical, radiographical, and histopathological data will assist in increasing the diagnostic certainty of HP. The new dichotomization of HP is thought to provide better prognostication for patients. This review provides clinicians with a current and evidence-based approach toward the management of patients with HP.

Rituximab therapy in a patient with steroid-refractory bird fancier's lung

A 62-year-old woman presented with a 3-month history of shortness of breath on exertion and dry cough. On examination, she was noted to have fine end-inspiratory crepitations over the upper zone of the lungs. Pulmonary function tests (PFTs) showed a restrictive defect. Initial chest radiography revealed diffuse reticular interstitial shadowing while high-resolution CT scan of the thorax showed fibrotic changes. Avian precipitins were also highly positive for pigeons, parrots and budgerigars. Taking into account these results, the patient was diagnosed with hypersensitivity pneumonitis. Antigen avoidance, oral glucocorticoids and azathioprine achieved an initial improvement in PFTs and symptoms; however, the patient still deteriorated, requiring long-term oxygen therapy. While working the patient up for lung transplantation, rituximab was given to good effect (acting as a bridging therapy) as it achieved symptomatic relief and stabilisation of her PFTs.

Assessment and Management of Occupational Hypersensitivity Pneumonitis

The diagnosis and treatment of occupational hypersensitivity pneumonitis (OHP) remain complex and challenging in the absence of diagnostic gold standards or clinical guidelines. This review provides an update of the recent literature regarding the different presentations of OHP and the diagnostic yield and value of the diagnostic tests currently available, which include occupational and medical history, laboratory tests (serum-specific immunoglobulins, environmental sampling), imaging, bronchoalveolar lavage, transbronchial biopsy, transbronchial cryobiopsy, surgical lung biopsy, and specific inhalation challenges. These tools provide a precise differential diagnosis within the framework of interstitial lung diseases. However, among the chronic fibrotic forms, distinguishing OHP from sarcoidosis, nonspecific interstitial pneumonia and idiopathic pulmonary fibrosis remains a diagnostic challenge. Avoidance of exposure is pivotal for OHP management, whereas corticosteroids are fundamental in the pharmacological approach to this disease. In addition, studies describing the long-term benefits of immunosuppressive and antifibrotic agents have increased the use of these treatments in OHP.

Current Diagnosis and Management of Hypersensitivity Pneumonitis

Hypersensitivity Pneumonitis (HP) one of the most common interstitial lung diseases (ILDs) is characterized by exposure to an inhaled inciting antigen that leads to a host immunologic reaction determining interstitial inflammation and architectural distortion. The underlying pathogenetic mechanisms are unclear. The absence of international shared diagnostic guidelines and the lack of a "gold-standard" test for HP combined with the presence of several clinical and radiologic overlapping features makes it particularly challenging to differentiate HP from other ILDs, also in expert contests. Radiology is playing a more crucial role in this process; recently the headcheese sign was recognized as a more specific for chronic-HP than the extensive mosaic attenuation. Several classification proposals and diagnostic models have been advanced by different groups, with no prospective validation. Therapeutic options for HP have been limited to antigen avoidance and immunosuppressant drugs over the last decades. Several questions about this condition remain unanswered and there is a need for more studies.