Post-streptococcal Hemophagocytic Lymphohistiocytosis in an Immunocompetent Adult.

Secondary hemophagocytic lymphohistiocytosis (HLH) is a rare and life-threatening hyperinflammatory syndrome that can occur after acute infection, predominantly caused by viruses. Due to its nonspecific presentation and clinical overlap with conditions like sepsis, HLH is frequently underrecognized in adults. We present the case of an immunocompetent adult admitted with undifferentiated shock, which rapidly progressed to multi-organ failure. Upon further investigation, the patient was diagnosed with HLH, and a comprehensive infectious workup revealed streptococcal pharyngitis as the precipitating cause. This case emphasizes the importance of recognizing HLH in the differential diagnosis in immunocompetent adults with pharyngitis presenting with shock, as early recognition is crucial for timely intervention and improved outcomes. Additionally, we review the current literature to characterize the reported infectious causes of HLH in immunocompetent adults in order to highlight the importance of having a low index of suspicion and conducting a comprehensive infectious workup.