A CBC shows Hgb 82 g/L, Hct 0.290/L, RBC 2.7 x 10^12/L, WBC 12.5 x 10^9/L, PLT 230 x 10^9/L, MCV 88 fL, MCH 29 pg, MCHC 330 g/L, RETIC 12%, uBIL 50 μmol/L, LDH 600 U/L, DAT 4+ at RT, DDAT 3+ C3D, Antibody Screen Anti-P, Urine BLOOD 2+. What is the presumptive diagnosis?

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Multiple Choice

A CBC shows Hgb 82 g/L, Hct 0.290/L, RBC 2.7 x 10^12/L, WBC 12.5 x 10^9/L, PLT 230 x 10^9/L, MCV 88 fL, MCH 29 pg, MCHC 330 g/L, RETIC 12%, uBIL 50 μmol/L, LDH 600 U/L, DAT 4+ at RT, DDAT 3+ C3D, Antibody Screen Anti-P, Urine BLOOD 2+. What is the presumptive diagnosis?

Paroxysmal Cold Hemoglobinuria is a hemolytic anemia caused by a biphasic anti-P antibody (Donath-Landsteiner–type) that fixes complement on cold exposure and causes intravascular hemolysis when warmed. The key clues are a direct antiglobulin test positive for complement (C3d) but not IgG, and an anti-P antibody detected on screening. Here the patient has clear evidence of intravascular hemolysis (low hemoglobin with reticulocytosis, elevated LDH, and indirect bilirubin), hemoglobinuria (urine blood positive), and a DAT showing C3d with anti-P activity. This pattern distinguishes it from warm AIHA, which would usually show IgG on the DAT, and from pancytopenia, which would involve multiple cytopenias rather than isolated RBC hemolysis.

Paroxysmal Cold Hemoglobinuria is a hemolytic anemia caused by a biphasic anti-P antibody (Donath-Landsteiner–type) that fixes complement on cold exposure and causes intravascular hemolysis when warmed. The key clues are a direct antiglobulin test positive for complement (C3d) but not IgG, and an anti-P antibody detected on screening. Here the patient has clear evidence of intravascular hemolysis (low hemoglobin with reticulocytosis, elevated LDH, and indirect bilirubin), hemoglobinuria (urine blood positive), and a DAT showing C3d with anti-P activity. This pattern distinguishes it from warm AIHA, which would usually show IgG on the DAT, and from pancytopenia, which would involve multiple cytopenias rather than isolated RBC hemolysis.

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