1465: Unusual Presentation of Acute Lymphoblastic Leukemia Masquerading as Sepsis With Lactic Acidosis

Introduction: Acute lymphoblastic leukemia (ALL) is a malignant proliferation of lymphoid precursors, most commonly seen in children. In adults, ALL is less common, comprising 15–25% of leukemias. Prognosis is worse in adults, especially with high-risk cytogenetic features like the Philadelphia chromosome. ALL often presents with nonspecific symptoms such as fever, fatigue, weight loss, and bone pain. Common hematologic findings include anemia, thrombocytopenia, and neutropenia, often with bleeding and organomegaly. Rarely, ALL presents atypically, mimicking systemic inflammatory responses seen in sepsis. Persistent lactic acidosis without an infectious source should prompt consideration of alternate diagnoses, including hematologic malignancy. Description: A 32-year-old woman with morbid obesity (BMI 54) presented with several days of fever, nonproductive cough, facial swelling and pain, and diarrhea. She was tachycardic, and CT angiogram of the chest showed bilateral infiltrates and hilar lymphadenopathy, raising concern for pneumonia. Labs showed persistent lactic acidosis (lactate 4–5 mmol/L) despite fluids, mild transaminitis, and atypical lymphocytes. Broad infectious workup—including viral panel, HIV, hepatitis, and urine antigens—was negative. Despite 10 liters of IV fluids, lactate rose to 11 mmol/L. Other findings included hypercalcemia with low parathyroid hormone and vitamin D. Otolaryngology evaluation ruled out surgical sinusitis, and antibiotics were escalated due to lack of improvement. Flow cytometry revealed an aberrant T-cell population (28%), concerning for T-cell neoplasm. While initial oncology evaluation was reassuring, final flow cytometry confirmed T-cell ALL. The patient was transferred for definitive oncologic care. Discussion: This case highlights how ALL can masquerade as sepsis, particularly with infection-like symptoms and abnormal labs. Lactic acidosis may reflect the Warburg effect, while hypercalcemia may be cytokine- or PTHrP-mediated. The absence of infection, persistent metabolic derangements, and atypical lymphocytes led to further hematologic workup. Prompt recognition of malignancy in such cases is crucial to avoid delay in life-saving treatment.