Differential Diagnosis for Pseudohyperkalemia

The following differential diagnosis is based on the provided patient scenarios and focuses on identifying pseudohyperkalemia, which refers to falsely elevated serum potassium levels not reflective of true hyperkalemia.

• Single Most Likely Diagnosis:

  • LB, a 30-year-old female with newly diagnosed chronic myeloid leukemia. The high white blood cell count (65 K/cu mm) can lead to pseudohyperkalemia due to the release of potassium from white blood cells during or after blood sampling, especially if there is significant leukocytosis.

• Other Likely Diagnoses:

  • XW, a 43-year-old female with a history of inflammatory bowel disease. Although her platelet count is low (70 K/mm3), which might not directly cause pseudohyperkalemia, the presence of other laboratory abnormalities and the clinical context could suggest other factors contributing to potassium level fluctuations.
  • PR, an 82-year-old female with severe myalgias and elevated creatine kinase (652 international units/L). Muscle damage can release potassium, but in the context of pseudohyperkalemia, this would be more relevant if the blood sample was hemolyzed or if there was significant delay in processing, which is not directly indicated.

• Do Not Miss Diagnoses:

  • RT, a 70-year-old male with small cell lung cancer receiving chemotherapy. While his presentation includes hyperkalemia (serum potassium 6 mmol/L), the critical aspect here is the potential for true hyperkalemia, especially in the context of malignancy and possible renal impairment. Tumor lysis syndrome (TLS) could be a concern, given the elevated uric acid and phosphorus levels, which would be a life-threatening condition if missed.

• Rare Diagnoses:

  • Thrombocytosis or extreme thrombocytopenia leading to pseudohyperkalemia, though this is less likely given the provided scenarios.
  • Factitious hyperkalemia due to laboratory error or sample contamination, which, although rare, should always be considered in cases where results do not align with clinical expectations.

Each patient's scenario presents unique factors that could influence potassium levels, but the key to diagnosing pseudohyperkalemia lies in recognizing laboratory or pre-analytical errors that could falsely elevate serum potassium readings. The clinical context, including recent diagnoses, treatments, and laboratory results, guides the differential diagnosis.