A fatal threat: Pneumocystis jirovecii pneumonia with rapidly progressive interstitial lung disease in anti-MDA5-positive dermatomyositis—a case report

Pneumocystis jirovecii pneumonia (PJP) is a respiratory infection caused by Pneumocystis organisms, representing an opportunistic fungal infection. The clinical occurrence of PJP combined with rapidly progressive interstitial lung disease (RP-ILD) in dermatomyositis (DM) have also been reported occasionally, but patients with this combination of conditions experience rapid disease progression and high mortality rates. We reported a 70-year-old female patient with dyspnea and fever, detailing her laboratory tests, computed tomography (CT) findings and bronchoalveolar lavage fluid findings. The patient's main clinical manifestations were dyspnea and fever. CT scans revealed scattered reticular opacities and ground-glass opacities in both lungs and metagenomic next-generation sequencing (mNGS) of the bronchoalveolar lavage fluid detected Pneumocystis jirovecii. Laboratory tests revealed positive anti-MDA5 antibodies during hospitalization. The patient was treated with high-flow oxygen therapy and methylprednisolone upon admission. Subsequently, the patient received mechanical ventilator support and was administered trimethoprim-sulfamethoxazole (TMP-SMX), plasma exchanges and immunoglobulin treatment. The patient's fever subsided, but respiratory failure and interstitial lung disease continued to progressively worsen. Ground-glass opacities, mixed ground-glass opacities, consolidations and reticular opacities were significantly more pronounced than on admission, indicating RP-ILD changes post-treatment. The patient succumbed after 13 days of treatment. PJP complicated by rapidly progressive interstitial lung disease can be fatal in patients, emphasizing the critical importance of early identification of PJP and prompt initiation of anti-PJP treatment. It is crucial to recognize that some MDA5+ DM patients may not present with the typical rash, and in certain cases, RP-ILD may be the primary manifestation. Therefore, early screening for anti-MDA5 antibodies is essential for patients presenting with unexplained early-stage RP-ILD.