Case 72

1. Presented by Karin Miller MD

An adult patient with no significant past medical history presented to their primary care physician with leg pain, fevers, night sweats, and lymphadenopathy. Initial laboratory results showed:

White Blood Cell Count: 161 K/cu mm (ref: 4.5-11 K/cu mm)
Hemoglobin: 7.8 g/dL (ref: 13.9-16.3 g/dL)
Hematocrit: 27% (41-53%)
Platelets: 51 K/cu mm (150-350 K/cu mm)

A manual differential showed that 82% of cells were blasts with the following morphology:

Peripheral blood flow cytometry showed (see flow plots) that 90% of the cells were phenotypically abnormal B cell precursors consistent with B-cell ALL. The cells showed dim-to-negative CD45 and expressed CD19 (heterogeneous), CD10, and CD38 as well as CD200 and CD20 (partial). They lacked kappa and lambda surface light chains.

Initial chemistry studies showed:
Na: 145 mmol/L (ref: 135-148 mmol/L)
K: 4.0 mmol/L (ref: 3.5-5.1 mmol/L)
Cr: 1.2 mg/dL (ref: 0.6-1.3 mg/dL)
Phosphorus: 4.0 mg/dL (ref: 2.7-4.5 mg/dL)
Ca: 9.2 mg/dL (ref: 8.4-10.5 mg/dL)
Uric Acid: 4.2 mg/dL (ref: 3.5-7.2 mg/dL)
Lactate Dehydrogenase: 1392 U/L (ref: 118-273 U/L)

Which of the following statements is incorrect regarding lactate dehydrogenase (LDH)?