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We read with great interest the article by Gianfrancesco et al concerning characteristics associated with hospitalisation for COVID-19 in people with rheumatic disease: data from the COVID-19 Global Rheumatology Alliance physician-reported registry. In this study, the authors mentioned that glucocorticoid exposure of ≥10 mg/day is associated with higher odds of hospitalisation and antitumour necrosis factor with decreased odds of hospitalisation in patients with rheumatic disease.1 We also aimed to present a case of microscopic polyanitis (MPA) with a diagnostic challenge with COVID-19 pneumonia. A previously healthy man in his 70s, who had complaints of malaise, fever, cough, tachypnea, dyspnoea was admitted to the emergency. Chest CT (CCT) scan revealed peripheral focal ground-glass opacities (GGOs) and infiltrations in the lower and upper lobes on the right and the left middle zones (figure 1). The patient was admitted to the intensive care unit with a prediagnosis of COVID-19 pneumonia and was intubated due to severe acute respiratory failure. Two nasopharyngeal swabs had negative RT- PCR for SARS-CoV-2. During his critical care, haemoptysis was developed, and the patient was observed to have proteinuria up to 8 g/day and active urinary sedimentation and was diagnosed with pulmonorenal syndrome. Immunofluorescence antineutrophil cytoplasmic antibody (ANCA) test was studied, and it was positive as p-ANCA. Also, ELISA ANCA was found to be positive against myeloperoxidase. The patient was diagnosed with MPA, and pulse steroid, plasma exchange, intravenous immunoglobulin (IVIG) and renal replacement therapy were given.
Clinical manifestations of patients with COVID-19 are varied. Symptoms such as fever, cough, tachypnea and shortness of breath can be seen. Peripheral, bilateral, GGO and multifocal GGO of rounded morphology with or without consolidation or visible intralobular lines (‘crazy-paving’) are the typical CCT findings of COVID-19 pneumonia.2 These radiological findings are non-specific for COVID-19 and can be seen in pneumocystis pneumonia; viral pneumonia, such as herpes, cytomegalovirus and influenza; and also in rheumatological conditions, including ANCA-associated vasculitis and sarcoidosis.3 While these CCT findings are characteristic for COVID-19, no tomographic findings are a gold standard. In the USA and many other countries, it is recommended not to use CCT for screening or diagnosis of COVID-19 pneumonia.4 However, CCT is still used for the first evaluation due to its easy access and rapid results in most countries. Patients may have evident tomographic findings even if they are asymptomatic. In a study in which 104 SARS-CoV-2-infected people were analysed, 17 (52%) of 33 asymptomatic patients had abnormal CCT findings, and most of them had GGO.5 However, in some cases, such as autoimmune disorders, GGOs cause confusion in differential diagnosis.
MPA is a necrotising vasculitis that usually affects small vessels of the skin, lungs and kidneys, with little or no immune deposits (pauci-immune). The lung is involved in a significant proportion of patients. The most common findings in CCT of MPA are GGO, reticulation, honeycombing and emphysematous changes. According to the results of a Japan study, of 78 patients with MPA with interstitial pneumonia without emphysematous changes, 46 (61.5%) had GGO.6
The exact differentiation of COVID-19 pneumonia and MPA is very important, since the treatment modalities of these two entities are almost the opposite. Alveolar haemorrhage observed in MPA and other necrotising vasculitis is seen as consolidation and GGO. Because peripheral and bilateral GGOs are also one of the most characteristic findings of COVID-19 pneumonia, some clinical and laboratory tips may be useful to distinguish them. Especially in patients with haemoptysis, proteinuria and urine casts in urinalysis, the clinician should be alert about MPA as a member of pulmonorenal syndrome. In addition, in patients whom respiratory distress palliated first, RT-PCR and ANCA tests will be useful to differentiate these two conditions.
Contributors SK: concepts, design, definition of intellectual content, literature search, data acquisition, manuscript preparation and manuscript editing. AC: patient treatment and follow-up. KA: patient treatment and follow-up, manuscript editing, manuscript review. HAS: patient treatment and follow-up.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.
Patient consent for publication Parental/guardian consent obtained.
Provenance and peer review Not commissioned; internally peer reviewed.
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