Abnormal erythrocyte morphology Rouleaux formation 2018-05-19T15:09:54Z Increased rouleaux formation Increased amount of stacking of erythrocytes into long chains. Rouleaux (singular: rouleau) is derived from a French word that can refer to a stack of coins put into a cylindircal paper roll. Rouleaux formation is observed with increased serum proteins, particularly fibrinogen and globulins, and represents the cause of increased erythrocte sedimentation rate because rouleaux sediment more readily than isolated red blood cells.