Paroxysmal cold hemoglobinuria (PCH) peripheral blood smear findings

These Wright-Geimsa-stained images from the peripheral blood smear of a patient with paroxysmal cold hemoglobinuria (PCH) illustrate RBC rosetting and erythrophagocytosis. The patient was admitted with chills, myalgias, jaundice, and black urine. The hemoglobin was 9.9 g/dL, total bilirubin 7.7 mg/dL, LDH 2204 U/L, and ferritin of 41,291 ng/mL. The direct antiglobulin test was positive for C3 and negative for IgG. The cold agglutinin screen was negative. Donath-Landsteiner testing was positive for biphasic hemolysin, with hemolysis occurring at 37°C after incubation at 4°C.

(A) RBC rosettes around neutrophils

(B) RBC couplets

(C) Neutrophils phagocytosing RBCs

These blood smear findings have high specificity for PCH but low sensitivity.