Our patient is a 3 year-old female who was previously healthy. Four months prior to hospitalization she began experiencing fatigue, recurrent fevers, progressive muscle weakness, and behavioral changes. The week prior to admission, she had decreased urine output, increased abdominal girth and respiratory distress. She was admitted to a community hospital for possible pneumonia. After 3 days, she was transferred to a tertiary center for oncologic assessment. There, her physical examination was concerning for a tender right axillary lymph node and hepatosplenomegaly. A chest radiograph demonstrated diffuse airspace opacities. PCR studies identified both rhinovirus and mycoplasma in nasal pharyngeal swabs. Twenty-four hours after arrival she developed hypoxemic respiratory failure requiring tracheal intubation and mechanical ventilation. This was complicated by an aspiration event and subsequent cardiopulmonary arrest, requiring resuscitation. Multiple subspecialties convened to facilitate an underlying diagnosis. HLH was considered given her hepatosplenomegaly, cytopenias, elevated CRP and normal ESR in the context of documented infection. Table 1 presents key HLH laboratory markers ordered at onset and their results. MAS, possibly associated with sJIA, was also considered despite the absence of arthritis, because of an intermittent, pink, net-like rash in the preceding weeks. Bone marrow evaluation was performed soon after her admission and demonstrated only rare hemophagocytes, similar to those seen in children with an underlying infection [5] .