The value of metagenomic next-generation sequencing in bronchoalveolar lavage fluid samples of anti-MDA5-positive dermatomyositis patients

Dear Editor, Anti-melanoma differentiation-associated gene 5 antibody-positive DM (anti-MDA5-positive DM) is a special subtype of myositis often combined with rapidly progressive interstitial lung disease, which has received increasing attention due to its poor prognosis and high mortality. A recent study reported a close relationship between anti-MDA5-positive DM and infection [1]. However, real-world clinical information is limited in those patients. Metagenomic next-generation sequencing (mNGS) is a sensitive detection technology that combines high-throughput sequencing with bioinformatic analysis for investigating an entire pathogen genome through RNA or DNA gene sequencing in a given sample. We retrospectively collected the data on 22 anti-MDA5-positive DM patients who completed mNGS testing with bronchoalveolar lavage fluid (BALF). Demographic data, including sex, age, detected pathogens, CD4 T cell counts and treatments, are shown in Table 1. Twenty-two patients were divided into two groups. In group 1, 10 patients underwent BALF mNGS testing prior to any treatment. Of these, four patients had bacterial infection, six had Pneumocystis jirovecii infection, four had viral infection and one had parasitic infection. In group 2, 12 patients showed aggravated dyspnoea symptoms after received glucocorticoids and immunosuppressants, underwent chest CT examination, and showed newly appearing pulmonary infiltrates compared with baseline. The BALF mNGS testing demonstrated six patients with bacterial infection. Of the seven patients with fungal infection, five were infected with P. jirovecii (71.4%). Eight patients had viral infection, with human betaherpesvirus 5 (cytomegalovirus, CMV) and human gammaherpesvirus 4 (Epstein–Barr virus; EBV) showing the highest detection rate (CMV: 87.5% and EBV: 50%). Finally, 11 patients had P. jirovecii infection, and for them the level of CD4 T cells was 283.1 (50.1) cells/µl, which was significantly lower than the level (452.5 (140.6) cells/µl) in patients without the P. jirovecii infection (P < 0.01, independent-sample t-test).