Thrombotic thrombocytopenic purpura and macrophage activation syndrome secondary to Sjögren's syndrome: a case report.

Sjögren's syndrome (SS) is a systemic autoimmune disorder frequently associated with diverse hematological manifestations. Immune-mediated thrombotic thrombocytopenic purpura (iTTP) and macrophage activation syndrome (MAS) represent rare, life-threatening complications, yet the consecutive occurrence of both conditions in the same SS patient is exceedingly rare. We report a 20-year-old female diagnosed with SS following drug-induced liver injury. In July 2023, she developed acute iTTP (0% ADAMTS13 activity, with positive inhibitory antibodies) shortly after the initiation of immunomodulatory therapy, which responded to plasma exchange and corticosteroids. In December 2023, following Mycoplasma pneumoniae infection, she presented with MAS, fulfilling seven of eight hemophagocytic lymphohistiocytosis (HLH)-2004 criteria. Management included high-dose methylprednisolone, etoposide, and ruxolitinib, followed by plonmarlimab (anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) antibody) under a clinical trial protocol. This unique case underscores the complexity of SS-associated hematological emergencies. Based on our findings, we propose a dual-pathway hypothesis for these complications: firstly, elevated IL-6 may facilitate the thrombotic cascade in SS-associated iTTP; secondly, the interferons-Janus kinases-signal transducer and activator of transcription (IFN-JAK-STAT) pathway's aberrant activation likely creates a mechanistic intersection that predisposes SS patients to MAS. While the efficacy of targeted agents like tocilizumab, ruxolitinib, and plonmarlimab appears promising in this context, these therapeutic avenues strictly warrant further systematic investigation through larger clinical cohorts.