Not Just Sjögren's: A Rare Life-Threatening Manifestation in a Pediatric Patient.

Macrophage activation syndrome (MAS), a severe hyperinflammatory state within the spectrum of hemophagocytic lymphohistiocytosis (HLH), is a life-threatening complication most commonly associated with rheumatologic disorders such as systemic juvenile idiopathic arthritis. Pediatric Sjögren's disease, however, is a rare and underrecognized etiology. We present the case of an eight-year-old female patient with no prior medical history who developed MAS in the setting of newly diagnosed Sjögren's disease, notably without classical sicca symptoms. Her course was marked by progressive systemic inflammation, multiorgan involvement, and laboratory findings suggestive of HLH/MAS. Diagnosis was confirmed through bone marrow biopsy and rheumatologic evaluation, and she responded favorably to immunosuppressive therapy with anakinra and corticosteroids. This case highlights the diagnostic challenges of MAS in atypical pediatric presentations and underscores the need for broader clinical suspicion in cytokine storm syndromes, particularly when established classification criteria are lacking.