<P> Rouleaux (singular is rouleau) are stacks or aggregations of red blood cells (RBCs) which form because of the unique discoid shape of the cells in vertebrates . The flat surface of the discoid RBCs gives them a large surface area to make contact with and stick to each other; thus forming a rouleau . They occur when the plasma protein concentration is high, and because of them the ESR (erythrocyte sedimentation rate) is also increased . This is a non-specific indicator of the presence of disease . </P> <P> Conversely the presence of Rouleaux is a cause of disease because it will restrict the flow of blood throughout the body because capillaries can only accept free flowing singular and independent red blood cells . The aggregations also known as "clumping" form as an allergic reaction to certain antibiotics and not necessarily because of disease . </P> <P> Conditions which cause rouleaux formation include infections, multiple myeloma, Waldenstrom's macroglobulinemia, inflammatory and connective tissue disorders, and cancers . It also occurs in diabetes mellitus and is one of the causative factors for microvascular occlusion in diabetic retinopathy . </P> <P> Acute - phase proteins, particularly fibrinogen, interact with sialic acid on the surface of RBCs to facilitate the formation of rouleaux . An increase in the ratio of RBCs to plasma volume, as seen in the setting of polycythemia and hypovolemia, increases rouleaux formation and accelerates sedimentation . Rouleaux formation is retarded by albumin proteins . </P>

Causes of rouleaux formation of red blood cells