Are mushroom‐shaped erythrocytes an indicator of COVID‐19?

Abstract

Since the beginning of the COVID-19 pandemic, many reports have documented the haematological impact of SARS-CoV-2 infection focusing on leucocytes and platelets. Following the observation of intriguing red blood cell morphology in a patient with COVID-19, we systematically reviewed the blood films of 49 additional patients in order to seek potential ‘suggestive’ erythrocyte alterations in a cohort of 50 individuals. A 55-year-old man was admitted to the Intensive Care Unit (ICU) with acute respiratory distress syndrome, following a positive nasopharyngeal swab for SARS-CoV-2 3 days previously, in the context of a mild cough and flu-like symptoms. Although respiratory insufficiency rapidly required mechanical ventilation, evolution was favourable within 7 days, with a progressive decrease in oxygen support. On admission to the ICU, his full blood count showed: haemoglobin concentration (Hb) 121 g/l, MCV 92 fl, MCHC 330 g/l, WBC 6·8 × 109/l, lymphocytes 0·4 × 109/l and platelets 220 × 109/l. The blood film showed mild anisocytosis, polychromasia and infrequent, but very evident, mushroom-shaped erythrocytes (‘pincer cells’) (central black-bordered image, May–Grünwald–Giemsa stain, ×40 objective). In order to investigate this interesting observation, we systematically reviewed the blood films of 49 additional, concomitantly hospitalised patients with COVID-19, regardless of the severity of the disease (31 were in ICU). There were 36 males and 14 females, with a median age of 64 years and median delay between the positive nasopharyngeal swab and the reviewed blood film of five days. None had a personal history of an erythrocyte disorder. Median blood count data were: RBC 3·8 × 1012/l, Hb 111 g/l, MCV 92 fl, MCHC 320 g/l, WBC 8·9 × 109/l, lymphocytes 0·9 × 109/l and platelets 253 × 109/l. Abnormal red cell morphology was found in all 50 patients, in particular, anisocytosis, spherocytes, stomatocytes and polychromasia, in 33, 26, 17 and 15 patients respectively. Strikingly, a few mushroom-shaped cells were evident in 33 patients (66%) (mosaic, each image corresponding to a single patient). Irregularly contracted cells were rarely seen. These findings suggest that SARS-CoV-2 infection may have a significant impact on red cell physiology, with a role for oxidative stress. Pincer cells are a characteristic feature of hereditary spherocytosis associated with Protein Band-3 deficiency; it is less well known that they may also be observed in oxidant-induced haemolysis, due to the removal of two Heinz bodies. Their presence in two-thirds of patients with SARS-CoV-2 infection suggests a possible role for oxidative stress in the pathophysiology of the disease.

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