A 16-year-old boy is brought to the emergency department due to a week of fever, dry cough, and weakness. Examination shows diffuse lymph node enlargement, mild hepatosplenomegaly, and scattered petechiae on the extremities. The testicles are normal and no neurologic abnormalities are present. Laboratory results are as follows: Peripheral blood smear reveals extensive blasts, and subsequent flow cytometry reveals T cell markers. A diagnosis of acute lymphoblastic leukemia is made. The patient is initiated on intravenous fluids, allopurinol, and combination chemotherapy. The following day, he develops nausea. Cardiac monitoring shows frequent premature ventricular beats. Repeat laboratory evaluation reveals leukocytes are 52,000/mm³, blood urea nitrogen is 34 mg/dL, serum creatinine is 2.1 mg/dL, and lactate dehydrogenase level is 12,000 U/L. Which of the following additional results are expected in this patient?

Question

A 16-year-old boy is brought to the emergency department due to a week of fever, dry cough, and weakness. Examination shows diffuse lymph node enlargement, mild hepatosplenomegaly, and scattered petechiae on the extremities. The testicles are normal and no neurologic abnormalities are present. Laboratory results are as follows:

Peripheral blood smear reveals extensive blasts, and subsequent flow cytometry reveals T cell markers. A diagnosis of acute lymphoblastic leukemia is made. The patient is initiated on intravenous fluids, allopurinol, and combination chemotherapy. The following day, he develops nausea. Cardiac monitoring shows frequent premature ventricular beats. Repeat laboratory evaluation reveals leukocytes are 52,000/mm³, blood urea nitrogen is 34 mg/dL, serum creatinine is 2.1 mg/dL, and lactate dehydrogenase level is 12,000 U/L. Which of the following additional results are expected in this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d432_5d48_bc81_c3dd2ae61a6c_MD0003_00 Tumor lysis syndrome (TLS) is common in patients with aggressive hematologic malignancies who are initiated on cytotoxic chemotherapy or immunotherapy. Large tumor burden (eg, some leukemias with elevated leukocyte count or lactate dehydrogenase levels) is a risk factor. Large-scale tumor cell death causes the massive release of intracellular products into the circulation, which results in potentially life-threatening electrolyte and metabolic abnormalities, including the following: Hyperphosphatemia: Tumor cells have up to 3 times more intracellular phosphate than normal cells. Therefore, massive tumor cell lysis is often associated with hyperphosphatemia. This results in systemic hypocalcemia due to increased calcium-phosphate precipitation, including in the renal tubules, leading to obstructing calcium-phosphate stones that can cause acute kidney injury. Hyperkalemia: Because potassium is primarily sequestered in the intracellular space, massive tumor cell lysis can cause hyperkalemia, which increases risk of cardiac arrhythmia. Hyperuricemia: Purine nucleic acids released from lysed tumor cells are metabolized by xanthine oxidase into uric acid. Because uric acid is poorly soluble in the acidic environment of the renal distal tubules and collecting system, it precipitates into obstructing uric acid stones, which are another cause of acute kidney injury. Most symptoms of TLS (eg, nausea, vomiting, diarrhea, muscle cramps, seizures, tetany) are also caused by electrolyte abnormalities. TLS prophylaxis typically includes intravenous fluids to flush phosphorus, calcium, and uric acid out of the kidneys and the administration of an agent (eg, allopurinol, rasburicase, febuxostat) to reduce uric acid levels. Educational objective: Patients with aggressive hematologic malignancies are at risk of tumor lysis syndrome when initiated on cytotoxic chemotherapy or immunotherapy. Intracellular contents are released into the serum, leading to hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia (due to calcium phosphate binding in the renal tubules). Major complications include acute renal injury (uric acid/calcium phosphate tubular injury) and cardiac arrhythmia. Prophylaxis with intravenous fluids and uric acid inhibitors reduces the risk of kidney injury.

A 16-Year-Old Boy Is Brought to the Emergency Department Due