Pediatric hypersensitivity pneumonitis: literature update and proposal of a diagnostic algorithm

Abstract

Hypersensitivity pneumonitis (HP) is a rare disease in childhood with the prevalence of 4 cases per 1 million children and an incidence of 2 cases per year. The average age of diagnosis at pediatric age is approximately 10 years. The pathogenesis of HP is characterized by an immunological reaction caused by recurrent exposure to triggering environmental agents (mostly bird antigens in children). The clinical picture of HP is complex and variable in children, often presenting in subacute forms with cough and exertion dyspnea. A diagnosis of HP should be considered in patients with an identified exposure to a triggering antigen, respiratory symptoms, and radiologic signs of interstitial lung disease. Blood tests and pulmonary function tests (PFT) support the diagnosis. Bronchoscopy (with bronchoalveolar lavage and tissue biopsy) may be needed in unclear cases. Antigen provocation test is rarely required. Of note, the persistence of symptoms despite various treatment regimens may support HP diagnosis. The avoidance of single/multiple triggers is crucial for effective treatment. No evidence- based guidelines for treatment are available; in particular, the role of systemic glucocorticoids in children is unclear. With adequate antigen avoidance, the prognosis in children with HP is generally favorable.

Fibrotic lung diseases in children

“…32 Gene variants at the TERT, RTEL, and PARN regions and major histocompatibility complex locus are related to increased susceptibility to fibrotic HP. 33…”

Unusual pediatric lung infections: imaging findings

“…Hypersensitivity pneumonitis, also previously known as extrinsic allergic alveolitis, is a complicated and heterogeneous interstitial lung disease caused by an excessive immune response to an inhaled antigen in susceptible individuals appearing as inflammation and/or fibrosis of the lung parenchyma and small airways. Hypersensitivity pneumonitis has a predilection for women and older individuals; however, it is the most frequent chronic interstitial lung disease in children [ 67 ]. Although more than 200 sensitizing antigens have been identified, bird antigens are by far the most common causative antigens in children [ 67 ].…”

“…Hypersensitivity pneumonitis has a predilection for women and older individuals; however, it is the most frequent chronic interstitial lung disease in children [ 67 ]. Although more than 200 sensitizing antigens have been identified, bird antigens are by far the most common causative antigens in children [ 67 ]. Accurate diagnosis of hypersensitivity pneumonitis is difficult and necessitates a detailed exposure history, as well as a multidisciplinary clinical, histopathologic, and radiologic evaluation.…”

Advances for pediatricians in 2022: allergy, anesthesiology, cardiology, dermatology, endocrinology, gastroenterology, genetics, global health, infectious diseases, metabolism, neonatology, neurology, oncology, pulmonology

“…Mastrorilli et al [15] address the 'hot topic' of hypersensitivity pneumonitis in children [16,17]. They underline that on the basis of a suggestive history, the diagnosis relies on respiratory signs and symptoms, pulmonary function tests, characteristic HRCT nodular opacities, serum specific IgG levels, response to elimination of eliciting factor.…”