Rouleaux (singular is rouleau) are stacks or aggregations of
red blood cells
Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek ''erythros'' for "red" and ''kytos'' for "holl ...
(RBCs) that form because of the unique
discoid shape of the cells in
vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
. 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
The erythrocyte sedimentation rate (ESR or sed rate) is the rate at which red blood cells in anticoagulated whole blood descend in a standardized tube over a period of one hour. It is a common hematology test, and is a non-specific measure of i ...
) is also increased. This is a nonspecific indicator of the presence of disease.
[Oxford Textbook of Medicine]
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.
Conditions that cause rouleaux formation include
infections
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
,
multiple myeloma
Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibodies. Often, no symptoms are noticed initially. As it progresses, bone pain, anem ...
,
Waldenström's macroglobulinemia,
inflammatory and connective tissue disorders, and
cancers
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal ble ...
. It also occurs in
diabetes mellitus
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level (hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
and is one of the causative factors for microvascular occlusion in
diabetic retinopathy
Diabetic retinopathy (also known as diabetic eye disease), is a medical condition in which damage occurs to the retina due to diabetes mellitus. It is a leading cause of blindness in developed countries.
Diabetic retinopathy affects up to 80 pe ...
.
Acute-phase proteins, particularly
fibrinogen
Fibrinogen (factor I) is a glycoprotein complex, produced in the liver, that circulates in the blood of all vertebrates. During tissue and vascular injury, it is converted enzymatically by thrombin to fibrin and then to a fibrin-based blood c ...
, interact with
sialic acid Sialic acids are a class of alpha-keto acid sugars with a nine-carbon backbone.
The term "sialic acid" (from the Greek for saliva, - ''síalon'') was first introduced by Swedish biochemist Gunnar Blix in 1952. The most common member of this ...
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
Polycythemia (also known as polycythaemia) is a laboratory finding in which the hematocrit (the volume percentage of red blood cells in the blood) and/or hemoglobin concentration are increased in the blood. Polycythemia is sometimes called erythr ...
and hypovolemia, decreases rouleaux formation and decreases sedimentation.
Rouleaux formation is retarded by
albumin proteins.
Rouleaux formations are also adopted by
spermatozoa
A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, ...
as a means of cooperation between genetically similar gametocytes so as to improve reproductive success through enhanced motility and, therefore, fertilization capacity—e.g., the
guinea pig
The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus '' Cavia'' in the family Caviidae. Breeders tend to use the word ''cavy'' to describe the a ...
.
Kinetics of Linear Rouleaux Formation
According to
Smoluchowski aggregation, the
kinetics of colloids is based on the assumption that each particle is surrounded by a "sphere influence". Single spherical particles which undergo
Brownian motion
Brownian motion, or pedesis (from grc, πήδησις "leaping"), is the random motion of particles suspended in a medium (a liquid or a gas).
This pattern of motion typically consists of random fluctuations in a particle's position ins ...
collide and sticking of particles happens. As aggregation proceeds, the average diffusion constant of the aggregate population decreases. The aggregation of red blood cells progresses in the same manner except that cells are
biconcave
A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...
rather than spherical.
See also
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Hemorheology
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Agglutinin
References
Further reading
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{{Abnormal clinical and laboratory findings
Abnormal clinical and laboratory findings for RBCs