Tocilizumab treatment for high-altitude antisynthetase syndrome-associated interstitial lung disease complicated by rectus sheath hematoma: interaction between hypofibrinogenemia and anticoagulation—a case report

Anti-Jo-1 antibody-positive antisynthetase syndrome (ASS) is frequently complicated by interstitial lung disease (ILD), and some patients respond poorly to glucocorticoids. The impact of chronic high-altitude hypoxia on the progression of ASS-ILD remains poorly documented and is currently only a hypothesis. Tocilizumab (TCZ) has shown efficacy in refractory ASS-ILD; however, TCZ-associated hypofibrinogenemia may contribute to bleeding risk in the setting of anticoagulation. Moreover, persistent elevation of creatine kinase (CK) after treatment is often attributed to ongoing myositis activity, but local tissue injury can also cause marked CK elevation and may influence therapeutic decisions. To the best of our knowledge, this is the first report of TCZ treatment for ASS-ILD in a patient residing at high altitude, documenting a life-threatening rectus sheath hematoma (RSH) associated with hypofibrinogenemia and concurrent anticoagulation. A 54-year-old Tibetan woman living at high altitude (3650 m) presented with a 7-day history of dry cough, dyspnea, and fatigue. Initial methylprednisolone treatment was effective; however, after discontinuation, she rapidly developed acute respiratory distress syndrome requiring endotracheal intubation. Anti-Jo-1 antibody positivity confirmed the diagnosis of ASS-ILD. Re-administration of methylprednisolone was ineffective. On day 15, due to a diagnosis of deep vein thrombosis (DVT), enoxaparin anticoagulation was initiated. On day 17, a single intravenous dose of TCZ was given, after which pulmonary lesions improved markedly, but fibrinogen (FIB) levels continued to decline. Six days after the start of anticoagulation (day 21), she developed large bilateral RSH with hemorrhagic shock. Following intensive treatment, her condition stabilized. Although interleukin-6 and C-reactive protein levels normalized, CK remained persistently elevated. Subsequent surgery revealed rectus sheath necrosis, and CK levels decreased significantly after surgery. TCZ may be an effective treatment option for glucocorticoid-refractory ASS-ILD at high altitudes; however, TCZ-associated hypofibrinogenemia may contribute to bleeding risk in the setting of anticoagulation. During TCZ therapy, regular monitoring of fibrinogen levels and individualized anticoagulation management are essential. The potential influence of high-altitude hypoxia on ASS-ILD progression remains a hypothesis and requires further investigation. In addition, elevated CK levels in patients with ASS should be carefully evaluated to distinguish active myositis from other causes, as this may directly affect treatment decisions.