Unusual Morphological and Automated Hematology Analyzer Features in 3 Cases of B-cell Malignancy-associated Type I Cryoglobulinemic Vasculitis.

Type I cryoglobulins are monoclonal immunoglobulins produced due to underlying hematological malignancy. Cryoglobulins spontaneously precipitate from serum and plasma at low temperatures and become soluble again on rewarming to 37 °C. Processing of blood at temperature lower than 37 °C in the laboratory may cause precipitation of cryoglobulins resulting in interferences in the automated cell counter analysis. We report three patients with cryoglobulinemic vasculitis wherein each case had different morphology of cryoglobulin precipitates on peripheral blood film, like needle shaped bluish-gray crystals, amorphous weakly basophilic extracellular deposits extraneously indenting red blood cells and basophilic neutrophilic inclusions respectively. The effect of cryoglobulins on two technologically different automated cell counters based on principles of impedance, Volume-Conductivity-Scatter (VCS) and fluorescence flow cytometry was assessed. This case series provides interesting insight into the varying morphological features of cryoglobulins on May-Grunwald-Giemsa stained blood films and interference caused by cryoglobulins in different automated cell counter analysis resulting in pseudo-leucocytosis, pseudo-thrombocytosis, abnormal histograms and scatterplots. Identification of these hematologic abnormalities and artifacts induced by cryoglobulins is necessary since it may be the first clue leading to the timely diagnosis of cryoglobulinemia and hence the underlying hematological malignancy, as in our cases. © Indian Society of Hematology and Blood Transfusion 2021.