Pancytopenia With Subsequent Diagnosis of Hemophagocytic Lymphohistiocytosis in a Middle-Aged Male.

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hyperinflammatory syndrome resulting from uncontrolled activation of the immune system. It is characterized by persistent fever, cytopenias, organomegaly, and a constellation of laboratory abnormalities including hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, and elevated soluble interleukin-2 receptor levels. HLH can be broadly classified into primary (familial) and secondary forms, the latter often triggered by infections, malignancies, autoimmune diseases, or other systemic insults. Despite advancements in diagnostic criteria and therapeutic strategies, HLH continues to carry high morbidity and mortality, largely due to its nonspecific and variable presentation that often leads to delays in diagnosis. Early recognition and prompt initiation of immunosuppressive therapy are crucial to improving outcomes. We are presenting a case of symptomatically gastrointestinal-dominant HLH presentation potentially due to an unusual trigger of TMP/SMX in an otherwise healthy adult male who presented with flu-like symptoms accompanied with abdominal pain.