Blood/Blood Cells and Cellular Components ›› Red Blood Cells ›› Abnormal Red Cell Agglutinate* Click Here for Full Size › Microscopic Features: Irregular overlapping aggregate of RBCs A cluster of overlapping RBCs (Non-linear overlapping RBCs) › Normal % blood-PB, marrow-BM, lymphoid tissue-LN: PB: None BM: None LN: None › May Resemble: Rouleaux Thick area of a blood smear giving rise to overlapping RBCs › Differential Diagnoses: Paroxysmal cold hemoglobinuria Cold agglutinins Elevated serum IgM M-spike as in Waldenstom 's macroglobulinemia Plasma cell neoplasm associated with monoclonal IgM › Classic Immunophenotype: N/A › Cartoon Image: Click and drag for direct comparison › Misc: This finding must be evaluated in the appropriate section of the peripheral blood smear (where RBCs are usually not touching each other). Typically associated with cold antibodies (usually IgM). Mostly due to reduced zeta potential (Note: the zeta potential between RBCs keeps them apart. Hence anything, usually relatively positively charged molecules such as immunoglobulins, that reduces this zeta potential will facilitate RBCs to aggregate or stack on top of each other).