Rouleaux formation (rouleaux RBCs)

Stacking of RBCs (like a stack of coins) which is usually due to an increase in the relatively positively charged blood proteins, such as immunoglobulins and fibrinogen which ultimately lead to a decrease in the zeta_potential between the RBCs and ultimately increase the chance of RBCs sticking to eachother. Rouleaux formation can be seen in multiple myeloma, and certain inflammatory conditions.