Which combination of electrolyte disturbances is most characteristic of tumor lysis syndrome?

• A. Hyperkalemia, hyperphosphatemia, hyperuricemia, hypocalcemia
• B. Hypokalemia, hypophosphatemia, hyperuricemia, hypercalcemia
• C. Hyperkalemia, hypophosphatemia, hypouricemia, hypercalcemia
• D. Hypokalemia, hyperphosphatemia, hyperuricemia, hypercalcemia

Answer: (A)

When tumor cells break open, their insides spill into the bloodstream. Potassium leaks out, giving hyperkalemia; phosphate leaks out, causing hyperphosphatemia; nucleic acids are broken down into uric acid, leading to hyperuricemia. The excess phosphate binds calcium, precipitating with it and driving free calcium downward, which results in hypocalcemia. This combination — high potassium, high phosphate, high uric acid, and low calcium — is the hallmark pattern of tumor lysis syndrome. The other patterns don’t fit because they show opposite trends (like low potassium or phosphate, or high calcium) that TLS does not produce. This electrolyte picture also underpins the risk of arrhythmias and acute kidney injury, guiding urgent management with hydration, urate-lowering therapy, and careful electrolyte monitoring.