Hyperkalemia Versus Pseudohyperkalemia Without ECG Changes in Acute Blast Crisis Progressing to Tumor Lysis Syndrome

TL;DR

A patient with a blood disorder developed high potassium levels, which were confirmed as real and not due to lab error, leading to severe complications requiring urgent treatment.

Contribution

This case highlights the diagnostic challenge of differentiating true hyperkalemia from pseudohyperkalemia in patients with extreme leukocytosis.

Findings

Hyperkalemia was confirmed as real through serum and plasma potassium measurements.

The patient progressed to tumor lysis syndrome requiring hemodialysis and cytoreductive therapy.

Pseudohyperkalemia was ruled out despite high blast count and cell fragility.

Abstract

Hyperkalemia is critical to recognize, but distinguishing it from pseudohyperkalemia is essential to avoid unnecessary treatment. We present a 66-year-old male with a history of myeloproliferative disorder and chronic myelomonocytic leukemia (CMML) who developed hyperleukocytosis (white blood cell (WBC) 666 × 10⁹/L, 95% blasts) and severe hyperkalemia (9.4 mmol/L) without electrocardiogram (ECG) changes. Pseudohyperkalemia was considered but ruled out by measuring serum and plasma potassium levels along with using heparinized and non-heparinized tubes. Pseudohyperkalemia is more common in hematologic malignancies due to extreme leukocytosis, which leads to an increase in cell fragility and potassium leakage during sample handling. Despite initial medical therapy, hyperkalemia persisted, requiring emergent hemodialysis, leukapheresis, and cytoreductive treatment. He developed tumor lysis syndrome (TLS), necessitating rasburicase and continuous renal replacement therapy. This case underscores the challenges of hyperkalemia in hematologic malignancies and the importance of rapid differentiation from pseudohyperkalemia.

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