A 36‐year‐old Chinese man with a recent diagnosis of COVID‐19 infection was treated in the National Centre for Infectious Diseases, Singapore. He was found to have severe lymphopenia and moderate thrombocytopenia on admission to ICU and required ventilatory support. Peripheral blood smear performed in view of a rising MCV from 86 fL to 92 fL demonstrated cold agglutination and rouleaux formation, lymphopenia with few reactive lymphocytes and rare lymphoplasmacytoid cells (Image 1A,B, Wright stain, 100x objective). There was no significant anemia or biochemical haemolysis and direct agglutination test was negative. Antibody screen revealed anti‐I antibody, a cold agglutinin titer of 1:8 with a mycoplasma pneumoniae antibody titer of 1:160. Serum electrophoresis did not show a monoclonal antibody. Respiratory multiplex PCR for other common respiratory viruses was negative.

IMAGE 1 Open in figure viewer PowerPoint A, Lymphoplasmacytoid cell with red cell agglutination. B, Reactive lymphocyte with red cell agglutination

Reactive lymphocytes are frequently seen in COVID‐19 infection (unlike in SARS), while in mycoplasma pneumoniae infection cold agglutination is common. COVID‐19 coinfection with other common respiratory pathogens such as mycoplasma pneumoniae may exacerbate clinical symptoms, increase morbidity and may cause prolonged ICU stay if left undetected or untreated. Clinicians managing patients with COVID‐19 infection should be mindful of coinfections with common respiratory pathogens during this COVID‐19 outbreak and screen for these with appropriate microbiologic tests.