Abstract Introduction Diffuse idiopathic pulmonary neuroendocrine hyperplasia (DIPNECH) is a rare disease recognized as a precursor to pulmonary neuroendocrine tumors. It has a non-specific clinical presentation, making prompt diagnosis challenging. Bilateral pulmonary nodules are hallmark imaging findings for DIPNECH; however, diagnostic criteria based on imaging alone have not been fully established, necessitating histopathologic confirmation through lung biopsy. Here, we present a puzzling patient case who presents with progressive dyspnea and overlapping features of DIPNECH, nonspecific interstitial pneumonia (NSIP), and hypersensitivity pneumonitis (HP) across radiologic, histopathologic, clinical, and laboratory findings. Case Description A 71-year-old female with a history of chronic hypoxemic respiratory failure on 3L oxygen and carcinoid tumor on Lanreotide presented to the interstitial lung disease (ILD) clinic for evaluation. Her symptoms began about a year prior to this visit, with progressive dyspnea, and she was hospitalized shortly thereafter for hypoxic respiratory failure. A chest CT at that time was concerning for ILD and she subsequently underwent a surgical lung biopsy locally. During her visit, she reported worsening productive cough, polyarthralgia, and myalgias. She had no known exposure or medication changes. Physical exam was significant for inspiratory crackles and digital clubbing. Her laboratory work-up for autoimmune etiologies of ILD was positive for RNA-Polymerase-III (50), Anti-PM (23), and Anti-SSA-52-kD (21). High-resolution CT (HRCT) imaging revealed scattered ground-glass opacities and peripheral reticulations with a basilar predominance, moderate to severe air-trapping, and many scattered non-calcified pulmonary nodules. Review of her lung biopsy revealed subpleural fibrosis with honeycomb changes, fibroblastic foci, and multiple neuroendocrine tumors. Our multidisciplinary discussions concluded with a diagnosis of DIPNECH and connective tissue disease (CTD)-ILD overlap with recommendations to add mycophenolate mofetil to her treatment regimen. Discussion We present a patient with overlapping radiologic, histopathologic, and clinical features of DIPNECH, NSIP, and HP, making elucidation of primary disease etiology difficult. DIPNECH can rarely mimic NSIP or HP both clinically and radiologically, presenting with chronic progressive dyspnea and cough, and ground-glass opacities and mosaic attenuation on HRCT. Additionally, pulmonary nodules, often seen on HRCT in both DIPNECH and HP, can be challenging to differentiate. Lung biopsy further complicated the interpretation with the presence of subpleural fibrosis with honeycombing, fibroblastic foci, and neuroendocrine tumor cells. The patient’s progressive pulmonary symptoms, polyarthralgia, and myalgias in combination with positive autoimmune markers additionally raised concern for CTD-associated ILD. These overlapping and confounding features highlight the importance of an interdisciplinary diagnostic approach for patients presenting with ILD. This abstract is funded by: None
O’Bryant et al. (Fri,) studied this question.