A 66-year-old Chinese woman presented with non-productive intermittent dry cough and progressive dyspnea in the first 3 weeks. Then, she appeared DM-related skin rashes, including bilateral periorbital heliotrope rash and Gottron sign on the joints of the elbows, in the next one week. Chest high-resolution Computed Tomography (HRCT) demonstrated interlobular septal thickening and subpleural ground-glass opacities ( Figure 1A ). Laboratory examination found increased serum anti-MDA5 antibody titer(328.76 for normal range 200-250), with positive antinuclear antibody at titer of 1:80. She was referred to Department of Rheumatology one months after her symptom onset and was diagnosed with MDA5-DM.

A step-up treatment regimen was initiated immediately for the rapid progressive interstitial lung disease (RP-ILD) ( Figure 1A ), with a combination of high-dose methylprednisolone equivalent of 2 mg/kg/day (1000mg/day) for 3days, intravenous immunoglobulin 20 g/d for 5 days, intravenous cyclophosphamide at a dosage of 0.4 grams once weekly (QW), and oral tacrolimus 2mg/day. The patient was received high-dose intravenous methylprednisolone (160 mg/d for 2 weeks) in the following 20days of treatment ( Figure 2 ). Her skin lesion and fever disappeared. However, chest HRCT showed a rapid progression of interstitial lesions ( Figure 1A ), and she required invasive ventilation for worsening hypoxemia after transferred to intensive care unit (ICU). On ICU admission, we decided to treat the patient with tofacitinib(at a dose of 5 mg twice daily) as her salvage therapy after she failed former combination therapy.

After administration to ICU, multiple indicators were conducted at the start of treatment and subsequently tested every 3-5 days. In the initial stage of tofacitinib therapy, a transient improvement in lung parenchymal translucency was observed on chest radiograph ( Figure 1B ). The improvement in respiratory effort markers, including plateau pressure (Pplat), peak inspiratory pressure (Ppeak), and driving pressure, occured simultaneously ( Figure 1C ). These changes suggested a potential therapeutic benefit of JAK inhibition in ameliorating pulmonary involvement. However, approximately three weeks after initial tofacitinib treatment, interstitial lung injury unexpectedly progressed despite these promising initial signs. Both chest radiograph and above respiratory parameters underwent deterioration ( Figures 1B, C ), accompanied by a series of changes in laboratory indicators. Increasement of serum ferritin levels and Krebs von den Lungen-6 (KL-6) levels, as well as a marked decrease in peripheral blood lymphocyte count ( Figure 1D ), were parallelled with the aggravation of interstitial lung injury. In line with these deterioration, decreased static lung compliance (CstatL) and pulse oximetry-measured oxygen saturation index (SpO₂/FiO₂) were accompanied during the treatment period ( Figure 1E ).

Reports have documented the pivotal role of myeloid cells in triggering cytokine storms during the progression of RP-ILD worsens (5, 6). In the initial period of tofacitinib therapy, we observed percentages of CD45⁺CD16⁺ monocyte and CD45⁺CD206⁺ macrophage subsets(methods seen in Supplementary) maintaining stability in BALF ( Figure 3A ). However, as dyspnea progression, their accumulation accelerated ( Figure 3B ). Comprehensively, recent research has emphasized interferon(IFN) signaling pathways, including cytokines like IFN-γ and IFN-α (7), as key regulators of monocytes and macrophages in pulmonary disorders (8). As we expected, secretions of IFN-γ and IFN-α in BLAF reduced in the initial period of tofacitinib therapy, subsequently increased as interstitial lung disease progressed to uncontrollable levels afterwards ( Figure 3C ). Moreover, pervious study suggested that alveolar macrophage triggered the release of cytokines and chemokines in critical lung disease. We observed alterations in proinflammatory cytokines, particularly IL-1β and TNF-α, accompanying with monocyte/macrophage chemotaxis, including IL-5 and IL-12p70(methods seen in Supplementary). These immune biomarkers, which are associated with macrophage activity, demonstrated an initial transient decrease followed by a subsequent increase, similar with the accumulation of alveolar myeloid cells ( Figure 3D ). The comprehensive deep-immune atlas of RP-ILD suggest that pronounced myeloid-driven immune process and increased immune mediators are predominant immunological hallmarks of critical MDA5-DM patients.

Unfortunately, three weeks after initial tofacitinib treatment, she was complicated by worsening liver failure. Her respiratory status demonstrated continued decline despite ventilator support and she ultimately passed in the setting of pulseless electrical activity arrest due to hypoxemic respiratory failure.

From April 2022 to September 2023, our clinical investigation extended to another cohort of four patients diagnosed with MDA5-DM complicated by refractory RP-ILD ( Table 1 ). The mean age of disease onset was 46 years (range 24–61 years), three females and one males were included. They all had significant increased serum anti-MDA5 antibody titer(range from 319.5-584.46), and three female patients were anti-Ro52-positive. Chest HRCT scans all revealed an organizing pneumonia pattern with subpleural consolidation, from subpleural opacities at the initial period to wide consolidation as ILD progression.

Glucocorticoid is used as the first-line treatment in all four patients. The initial dose of methylprednisolone is dependent on the extent of disease severity. Among them, a high-dose methylprednisolone equivalent of 1–2 mg/kg/day(500-1000mg/day) of prednisone is administered in three patients with high disease activity, and a moderate dose (≤0.5 mg/kg/day of prednisone equivalent) of 160mg/day for case 3 with low disease activity. A combination of glucocorticoid with immunosuppressant therapy, including cyclophosphamide and tacrolimus, is also used in the initial treatment of three female patients as dyspnea progression. Meanwhile, intravenous immunoglobulin therapy has been established in three patients with high ILD activity. After all above triple combination therapy, JAK inhibition of oral tofacitinib(at a dose of 5 mg twice daily) were all administrated in these four refractory MDA5-DM patients ( Figure 2 ). After approximate 20 days of treatment, case2 and case 3 patients achieved clinically significant improvement accompanied with increase in the absolute peripheral lymphocyte number and SpO₂/FiO₂ ( Figure 4A ). Biomarkers for lung damage, including ferritin and Krebs von den Lungen‐6 (KL‐6), also decreased during disease remission ( Figure 4B ). Case 5 patients attained limited effectiveness in maintaining stable levels of peripheral lymphocyte count, oxygen index and biomarkers in the initial treatments. However, case 5 patient showed major improvement after 6 months of oral triple combination therapy ( Figures 4A, B ). Only case 3 was worsened 20 days after treatment. Case 3 patient showed significant decrease in the absolute peripheral lymphocyte number and SpO₂/FiO₂, with elevation levels of serum ferritin KL‐6 ( Figures 4A, B ).Eventually, her family gave up on treatment and discharged from hospital.

The serum interferon(IFN) signaling pathways related cytokines, IFN-γ and IFN-α, at the baseline were higher in case 3 than those three alive patients ( Figure 4C ). The changes in IFN-γ and IFN-α were parallel to the deterioration of peripheral lymphocyte count, oxygen index and biomarkers in case 3 patient ( Figures 4A–C ). The levels of IFN-related cytokines showed a tight link to the progression of ILD from initial to post-treatment of tofacitinib. Specifically, all three alive patients exhibited a pronounced therapeutic response to tofacitinib. The significant reduction in IFN-mediated cytokines in three alive patients suggests that by targeting JAK pathways, tofacitinib effectively modulates the immune response, mitigating the proinflammatory environment associated with DM and potentially ameliorating interstitial lung injury.