Rouleaux refers to the characteristic appearance of red blood cells forming "a stack of coins." It is usually associated with a high concentration of proteins, which changes the interaction between the erythrocytes.


Rouleaux is French for "roll" as in roll of coins.


The stacking of the red cells can be seen in a wet mount of whole blood. Dilution of the blood with normal saline reduces the protein concentration, and the rouleaux disappears.



(1) elevated monoclonal globulin (myeloma, macroglobulinemia)

(2) elevated polyclonal globulin (cirrhosis, chronic infection)

(3) elevated fibrinogen level

(4) elevation in other serum proteins

(5) following transfusion with high molecular weight dextrans or other macromolecules


Differential diagnosis:

(1) agglutinated red blood cells

(2) pseudostacking of red blood cells in thicker parts of the blood smear. True rouleaux should extend out to the feather edge.


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