A 40-year-old male presented to the emergency room with 7 days of fever and chills and 2 days of jaundice, nausea, and vomiting. On examination, he had a temperature of 101.8°F, tachycardia (110 bpm), and yellowish discoloration of the conjunctiva. Hematological tests showed hemoglobin of 12.2 g/dL, white blood cells of 6850/mm3, and thrombocytopenia (22,000/mm3). The Sysmex Xn-1000 hematology analyzer white blood cell differential (DIFF) (WDF) plot showed eosinophilia (9%) and a scattergram showing two neutrophil clusters—one normal, the other likely pigment-laden cells, overlapping the eosinophil zone, causing factitious eosinophilia. An abnormal blue-coded event appeared in the red blood cell (RBC) ghost region due to parasitized cells Figure 1B. The white cell nucleated (WNR; white blood cells and nucleated blood cells) plot revealed distinctive RBC debris clusters Figure 1D. These findings suggested parasitic infection.Figure 1: (A) Normal white blood cell differential scattergram: cell populations are separated by side fluorescence (Y-axis) and side scatter (X-axis): Lymphocyte (L magenta), monocytes (M green), neutrophils (P, cyan), eosinophils (E, red), and debris (blue). (B) Two neutrophil clusters (P, cyan) normal large one and another small (P) overlapping an eosinophil (red zone). (C) Normal white cell nucleated (white blood cells and nucleated blood cells) plot. (D) Distinctive red blood cell debris clustersBlood smear (thick/thin) examination confirmed Plasmodium vivax (P. vivax) with trophozoites and gametocytes Figure 2. The manual eosinophil count was 1%. The malarial antigen kit detects positivity for P. vivax-specific pan-lactate dehydrogenase Figure 2 inset. The patient was treated for P. vivax malaria and discharged in stable condition after 1 week.Figure 2: Peripheral blood smear (thin) revealed Plasmodium vivax trophozoites with pigment granules (red circle). The malarial antigen kit showed a P. vivax-specific positive band for pan-lactate dehydrogenase (inset)Factitious eosinophilia (pseudoeosinophilia) is defined by a discrepancy greater than 5% between manual and automated DIFF counts. In malaria, RBC lysis releases hemozoin pigment, which is phagocytosed by neutrophils. These pigment-laden neutrophils exhibit increased cytoplasmic granularity, demonstrate altered side scatter/fluorescence characteristics, and form separate clusters and cause pseudoeosinophilia on scattergram.1 Additionally, infected RBCs or RBC fragments containing parasite nucleic acid (debris) might provide abnormal signals in the WDF/WNR DIFF plot, resulting in double cluster and RBC debris flags, respectively. Double neutrophil clusters are characteristic but not specific to malaria. This is also seen in cases of myelodysplastic syndrome, granulocyte colony-stimulating factor therapeutic effects, toxic granules in severe infections, and sample artifacts.2 WDF DIFF plot abnormalities were more frequently observed in P. vivax (sensitivity 90%) than in Plasmodium falciparum (sensitivity 50%). The most common WDF DIFF plot finding was dual neutrophil populations (69%), followed by a rightward shift in the RBC ghost region (64.2%).2 A study demonstrated that isolated pseudoeosinophilia yielded a sensitivity of 39%, whereas abnormal DIFF findings showed a sensitivity of 52%.3 Sensitivity for malaria detection increased markedly when both WBC DIFF scattergrams and hematological abnormalities such as thrombocytopenia were assessed together.4,5 This combined approach emerged as the strongest predictor of malaria, as seen in our case. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
Majed Abdul Basit Momin (Thu,) studied this question.