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Zorluk: KolayPediatric Hematology and Oncology

A 7-year-old boy with newly diagnosed Burkitt lymphoma is started on induction chemotherapy. Within 24 hours, he develops lethargy, nausea, and decreased urine output. Laboratory studies show hyperkalemia, hyperphosphatemia, hypocalcemia, and elevated serum uric acid levels. Arrange the following pathophysiologic events in the correct chronological order leading to this patient's acute kidney injury.

  1. 1Rapid lysis of neoplastic cells following chemotherapy administration
  2. 2Massive release of intracellular potassium, phosphorus, and nucleic acids into the circulation
  3. 3Hepatic metabolism of purine nucleic acids into uric acid
  4. 4Precipitation of uric acid and calcium phosphate within the renal tubules
  5. 5Intratubular obstruction resulting in acute kidney injury

Cevap

Rapid lysis of neoplastic cells -> Massive release of intracellular contents -> Metabolism of nucleic acids into uric acid -> Precipitation of crystals in renal tubules -> Intratubular obstruction and acute kidney injury.
Tumor lysis syndrome (TLS) is an oncologic emergency characterized by the massive destruction of tumor cells, most commonly seen after initiating chemotherapy for high-grade hematologic malignancies like Burkitt lymphoma or acute lymphoblastic leukemia. The correct sequence of pathogenesis begins with the lysis of these neoplastic cells. This lysis causes a massive release of intracellular contents into the systemic circulation, specifically potassium, phosphorus, and nucleic acids. The purine nucleic acids are subsequently transported to the liver, where xanthine oxidase metabolizes them into uric acid, resulting in hyperuricemia. The high concentration of uric acid can precipitate in the acidic environment of the renal tubules. Additionally, the excess phosphate binds to circulating calcium, causing hypocalcemia and forming calcium phosphate crystals, which also precipitate in the kidneys. Ultimately, these crystals cause physical intratubular obstruction, leading to oliguria and acute kidney injury.

Adım Adım Çözüm

1
Identify the clinical syndrome presented in the vignette.
The patient has Tumor Lysis Syndrome (TLS) following chemotherapy for Burkitt lymphoma.
Burkitt lymphoma is a highly proliferative tumor, and the patient presents with the classic metabolic triad of TLS: hyperkalemia, hyperphosphatemia, and hyperuricemia (which causes secondary hypocalcemia).
2
Trace the origin of the metabolic abnormalities.
Chemotherapy causes cell lysis, releasing intracellular ions (potassium, phosphate) and purine nucleic acids into the extracellular space.
Malignant cells have high intracellular concentrations of these substances compared to extracellular fluid.
3
Determine the mechanism of acute kidney injury in this syndrome.
Purines are metabolized to uric acid, which precipitates in the kidneys along with calcium phosphate, causing mechanical obstruction.
Uric acid is poorly soluble in acidic urine, and calcium phosphate precipitates when the calcium-phosphorus product is elevated, leading to acute tubular injury.

Anahtar Kavram

Pathophysiology of Tumor Lysis Syndrome
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Pediatric Hematology and Oncology

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