By William Aird

Rouleaux formation in a 49-year-old man with rheumatoid arthritis. Note the stacked-coin appearance of red cells in several parts of the field. Overlap between red cells within the stacks may result in obscuring of central pallor (50x).

Red blood cell, cell arrangement Rouleaux formation
DefinitionArrangement of > 3 red cells in a linear or branched pattern resembling a stack of coins
DdxMay be seen with poor preparation of the smear or by viewing the thick area of a blood smear
Conditions associated with the red cell propertyConditions associated with an inflammatory response and acute phase reaction, multiple myeloma, certain malignant lymphomas
Mechanism of formationCaused by an increase in positively charged proteins, especially fibrinogen and immunoglobulins. The resulting stacking of red cells may lead to an increased erythrocyte sedimentation rate (ESR).
Source/authorWilliam Aird
Reviewed and edited byParul Bhargava