Erdheim-Chester disease.

Erdheim-Chester disease (ECD) is a rare but increasingly recognized multi-system disorder. Its diagnosis and treatment require integration of clinical information, imaging studies, and pathology studies. Of note, ECD can now be defined as a clonal myeloid disorder due to mutations which activate mitogen-activated protein kinase (MAPK) pathways and where an inflammatory milieu is important in the pathogenesis and clinical manifestations of the disease.

Macrophage activation syndrome in a patient with axial spondyloarthritis on adalimumab.

Macrophage activation syndrome (MAS) is a rare and potentially fatal condition characterized by excessive activation and uncontrolled proliferation of T lymphocytes and macrophages, leading to overwhelming systemic inflammation and cytokine release. MAS has been reported with viral infections, autoimmune disorders, malignancies, and medications. We describe a case of a patient with axial spondyloarthritis (axSpA) treated with adalimumab, who presented with MAS.