Influenza H1N1 virus-associated pneumonia often resembles rapidly progressive interstitial lung disease seen in collagen vascular diseases and COVID-19 pneumonia; CT-pathologic correlation in 24 patients

Differences in clinical characteristics and chest CT findings between severe and critical H1N1 pneumonia

INTRODUCTION

Critical H1N1 pneumonia patients usually have one of the symptoms such as respiratory failure, septic shock, multiple organ dysfunction, or other need for intensive care management, which are associated with high risk of mortality. It is essential to differentiate the severity of H1N1 pneumonia and take corresponding target treatments.

OBJECTIVES

We aim to investigate the differences in clinical characteristics and chest computed tomography (CT) findings between severe and critical patients with H1N1 pneumonia.

METHODS

A total of 27 patients diagnosed with H1N1 pneumonia from October 2018 to March 2019 were retrospectively analyzed, and the differences in clinical manifestations, laboratory tests, and chest CT findings between the severe group (15 patients) and the critical group (12 patients) were compared.

RESULTS

Frequency of dyspnea at rest was higher in critical group than that in severe group (P = 0.019). The neutrophil percentage was higher (P = 0.014) and the lymphocyte percentage was lower (P = 0.025) in critical compared with severe group. Bilateral lung involvement was the predominant pattern in both severe and critical patients, whereas the number of involved lobes in critical patients was more than that in severe patients (P = 0.024). Peripheral distribution was the predominant pattern in severe patients (40%), whereas more diffuse involvement of the lungs was observed in critical patients (83.30%). Ground-glass opacities and consolidation were the main CT findings in both groups, and prevalence of consolidation was higher in critical relative to severe group (83.30%).

CONCLUSION

Compared with severe patients, those with critical H1N1 pneumonia were more likely to present with dyspnea at rest and decreased lymphocyte percentage. Chest CT showed that diffuse bilateral involvement and higher prevalence of consolidation are associated with critical outcomes.

High-Resolution CT Findings of Myositis-Related Interstitial Lung Disease

Myositis-related interstitial lung disease presents with a wide variety of lesions, ranging from chronic to acute. It can be divided into two main forms by the types of onsets, namely, chronic to subacute type showing nonspecific interstitial pneumonia (NSIP) or NSIP with an organizing pneumonia (OP)/fibrosing OP (FOP) pattern and acute type showing acute lung injury (ALI) to diffuse alveolar damage (DAD) pattern. Anti-aminoacyl tRNA Synthetase antibody-positive cases mainly show an NSIP or FOP pattern, whereas anti-melanoma differentiation-associated gene 5 antibody-positive cases show ALI to DAD pattern. Bilateral consolidation with or without ground-glass opacification with lower lobe predominance is common as a major pattern in all types, but the distribution or extent is sometimes different. The early detection of findings that indicate a rapid progressive course is vital. Diffuse cranio-caudal distribution and multiple ground-glass opacifications with random distribution might indicate a poorer prognosis.