Signs of Leukemia in Infants and Toddlers: Understanding Fever Patterns and Underlying Causes

Fevers in infants and toddlers with leukemia often lack distinct characteristics, making early detection challenging. Unlike fevers caused by common viral or bacterial infections, elevated body temperature in pediatric leukemia cases may stem from non-infectious origins or secondary complications. Recognizing the underlying causes of fever is crucial for timely medical evaluation and diagnosis.

Two Primary Causes of Fever in Pediatric Leukemia

When a young child presents with persistent or recurrent fever, it's important to consider both infectious and non-infectious triggers—especially if symptoms don't respond to standard treatments. In cases of infantile leukemia, fever typically arises due to one of two main mechanisms: tumor-related (non-infectious) fever or infection-induced fever.

1. Tumor-Related Fever (Pyrexia of Unknown Origin)

In children with leukemia, abnormal white blood cells—known as blasts—multiply uncontrollably in the bone marrow. As these malignant cells break down, they release cytokines such as interleukin-1 (IL-1), tumor necrosis factor (TNF), and other inflammatory mediators into the bloodstream. These substances act as endogenous pyrogens, directly affecting the hypothalamus and triggering a systemic rise in body temperature.

This type of fever is often referred to as "tumor fever" or "neoplastic fever." It usually doesn't follow a consistent pattern—it can be intermittent, low-grade, or spike suddenly without chills or obvious infection signs. Because there's no active pathogen involved, antibiotics are ineffective, which can confuse initial diagnoses.

2. Infection-Induced Fever Due to Immune Suppression

Leukemia disrupts normal hematopoiesis—the process by which healthy blood cells are produced in the bone marrow. The uncontrolled proliferation of leukemic cells crowds out normal stem cells, leading to reduced production of functional immune cells like neutrophils and lymphocytes. This condition, known as immunosuppression, leaves infants highly vulnerable to infections.

Common pathogens—including bacteria, viruses, and fungi—can take advantage of this weakened defense system. Infections may occur in various parts of the body, such as the respiratory tract (pneumonia), urinary tract (UTI), skin, or even the bloodstream (sepsis). Each of these can present with fever that mimics routine childhood illnesses, further complicating early recognition of leukemia.

Fever patterns in these cases vary widely—there's no specific thermal signature that distinguishes them from ordinary infections. However, when fevers are prolonged, resistant to treatment, or accompanied by other warning signs like pallor, bruising, lethargy, or poor feeding, further investigation becomes essential.

Diagnostic Considerations: When to Suspect Leukemia

A fever alone is not enough to diagnose leukemia. Many common childhood conditions cause similar symptoms. However, when fever persists without a clear source, clinicians should evaluate the possibility of an underlying hematologic disorder.

Blood tests play a critical role in differential diagnosis. A complete blood count (CBC) can reveal abnormalities such as unusually high or low white blood cell counts, anemia (low hemoglobin), or thrombocytopenia (low platelets)—all potential red flags for leukemia. If results are inconclusive but clinical suspicion remains, additional testing such as peripheral blood smear analysis or bone marrow aspiration may be warranted.

Early detection significantly improves outcomes. Parents and caregivers should seek prompt medical attention if a child exhibits unexplained fatigue, frequent infections, easy bruising, bone pain, or swollen lymph nodes alongside persistent fever.

Conclusion: Awareness Saves Lives

While fever in infants and toddlers is common, its persistence or recurrence without an identifiable cause should never be ignored. Understanding the dual nature of fever in pediatric leukemia—both as a direct result of cancerous activity and as a consequence of compromised immunity—empowers parents and healthcare providers to act swiftly. Increased awareness, combined with timely diagnostic testing, can lead to earlier intervention and better long-term prognosis for affected children.