Clinical characteristics of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia

Rationale Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is characterised by diffuse bronchial hyperplasia of pulmonary neuroendocrine cells, which are situated within the walls of bronchi and bronchioles. Presenting symptoms are nonspecific and the clinical course varies, making diagnosis challenging. We sought to describe the clinical characteristics of patients with DIPNECH in a large multinational case series to guide and inform future care and research. Methods Data were collated from 18 international centres. Information collected included disease presentation, pulmonary function testing, histopathology, radiological patterns and outcomes. The relationship between clinical features, radiology and symptoms were explored in parametric and nonparametric group-wise analyses, univariate linear regressions, and multivariate binomial logistic regression. Results The mean±SD age of the 258 patients in this study was 63.3±10.6 years and 93.4% were female. Diffuse pulmonary nodules (98.8%) and mosaic attenuation (59.1%) were the most common radiological findings and 29.5% had obstructive spirometry with a mean±SDforced expiratory volume in 1 s (FEV₁)% pred of 69.0±23.7%. There was a significant association between the number of nodules and a reduction in FEV₁ % pred (p<0.001), while the presence of bronchial wall thickening on imaging was most closely associated with cough (OR 4.97, p=0.001) dyspnoea (OR 3.14, p=0.003) and bronchodilator responsiveness (OR 3.09, p=0.013). Approximately half of patients treated with inhaled beta agonist and corticosteroids (46.3%) or somatostatin analogue (54.1%) reported improvement in symptoms. Conclusions The presence of radiological bronchial wall thickening is associated with the presence of symptoms, while mosaic attenuation is correlated with airflow obstruction; hence, the presence of these radiological findings has the potential to guide possible treatment decisions.