Clinical features of adults with undiagnosed acute leukemia in the emergency department: A descriptive study

Acute leukemia is a life-threatening hematologic malignancy requiring early diagnosis, particularly in the emergency setting. However, initial clinical presentations in the emergency department (ED) remain poorly characterized, resulting in potentially delayed diagnosis. We aimed to describe the initial clinical presentations and major complications of adult patients with previously undiagnosed acute leukemia presenting to the ED.

We conducted a retrospective descriptive study at a tertiary care ED in Japan from January 2016 to December 2025. We included patients aged 16 years or older who were newly diagnosed with acute leukemia within 14 days of the ED visit. Patients were categorized into uncomplicated and complicated groups based on the presence of febrile neutropenia, intracranial hemorrhage, or leukostasis. We examined the frequency of the three common presenting symptoms (fever, dyspnea, and bleeding tendency) and the presence of major complications at ED presentation.

Of 49 patients with acute leukemia, 30 (61%) were in the uncomplicated group and 19 (39%) in the complicated group. Fever was the most frequent presenting symptom but was present in only 43% of uncomplicated patients. Among uncomplicated patients, 20% presented with none of the three common presenting symptoms, and 50% presented with only one. In complicated acute leukemia, chief complaints were frequently pain or altered mental status rather than the common symptoms.

A substantial proportion of adult patients with acute leukemia presenting to the ED had heterogeneous symptoms. Emergency physicians should maintain a low threshold for laboratory evaluation including peripheral blood smear.