The single-cell RNA sequencing (scRNAseq) analysis (24) of bronchoalveolar lavage fluid (BALF) from severe COVID-19 patients found abnormally low numbers of resident AM and an increase in 2 macrophage clusters that share expression of ficolin-1 (FCN1) and are distinguished by their relative expression of osteopontin (SPP1): FCN1+ and FCN1+SPP1+ clusters. The gene discussed is FCN1; the disease is COVID-19.