CLS 291 and 292 RBC and WBC MORPHOLOGY

only RBC morphology

describe a normal erythrocyte

- a discocyte due to biconcave shape and is 7-8 μm with an MCV of 80 - 100 fL

- area of central pallor (indent) is surrounded by a rim of pink-staining hemoglobin and roughly 1/3rd of the diameter of the cell

what is the general trend for when cells mature?

as cells mature, they go from a larger immature cell to a smaller mature cell (doesn’t apply to thrombocytes)

what is anisocytosis? how are the RBCs evaluated microscopically to confirm anisocytosis?

variation in red cell size (macrocytes, microcytes) with an RDW of >14.5% (suggests diff sizes of RBCs are present) and MCV is either less than 80 fL or more than 100 fL

- RBCs are compared with the nucleus of a normal small lymphocyte and normocytic RBCs are about the same size as the nucleus of small lymphocyte

what are microcytes (anisocytosis)?

RBCs have the diameter of <7.0 μm, MCV < 80fL, and usually hypochromic but can be normochromic

- if in the shape of spheres → microspherocytes and can appear hyperchromic

what are macrocytes (anisocytosis)?

RBCs have a diameter of >8.0 μm and a MCV of >100 fL with an adequate amount of Hb (normal MCHC 32-36% and normal [28 - 34 pg] to higher MCH)

- younger RBCs are larger than mature RBCs for 1 day then the spleen grooms them to normal size (reticulocyte count is up, the MCV can be up)

what is poikilocytosis?

used to describe nonspecific variation in shape of RBCs

- some shapes and sizes are characteristic of specific underlying hematological disorder or malignancies

- some morphology may be artifactual like from poorly made or improperly stained smears

what is an acanthocyte (spur cell)?

small spherical cells that does not have a central pallor with irregular thornlike projections (projections may have small bulklike tips)

- RBC membranes have altered lipid content due to increased free cholesterol accumulation leading to decreased fluidity in RBC membrane

- diseases → abetalipoproteinemia, alcoholic liver disease, disorders of lipid metabolism, post splenectomy, fat malabsorption, retinitis pigmentosa

what is a codocyte (target cell)?

thin, bell shaped cells with an increased surface area-to-volume ratio

- will look like a target cell with a bull’s eye in the center on a blood smear (bulls' eye is surrounded by an achromic zone and a thin outer ring of pink-staining Hb)

- can appear as artifacts when a wet smear is not dried correctly or made in high humidity environment

- diseases → hemoglobinopathies, thalassemias, obstructive liver disease, splenectomy, renal disease, iron deficiency anemia

what is a dacryocyte (tear drop cell)?

RBCs that are elongated on one end to form a teardrop

- formed when the RBCs containing inclusions traverse the spleen (remember spleen pits and culls) → area with the inclusion has difficulty passing through the splenic filter and the cell becomes stressed and cannot return to its normal shape

- diseases → myelophthisic anemias, primary myelofibrosis, thalassemia

what is a drepanocyte (sickle cell)?

elongated, crescent-shaped RBC with pointed ends… some forms have more rounded ends with a flat side (reversible)

- Hb is abnormal and polymerizes into rods in decreased O2 tension or decreased pH conditions → first forms a holly leaf shape and then as Hb polymerization continues, it changes to a sickle cell

- has increased mechanical fragility

- diseases → sickle cell disorders

what is an echinocyte (burr cell)?

smaller than normal RBCs (7-8 mcM) with regular, spinelike projections

- reversible meaning it can revert back to a discocyte

- can become a spherocyte due to the removal of the membrane spines in spleen

- common artifact in blood smears due to a “glass effect” when making smear and can appear within several days of storing blood at 4C

- true echinocytes thought to be related to an increase in the area of the outer leaflet of the RBC membrane

- diseases → liver disease, uremia, pyruvate kinase deficiency, peptic ulcers, cancer of stomach, heparin therapy

what is an elliptocyte (pencil or cigar cells)?

varies from elongated oval shapes (ovalocytes) to elongated rodlike cells with a central area of biconcavity with Hb concentration at both ends

- formed after cell leave the bone marrow (reticulocytes and young erythrocytes are normal in shape)

- mechanism of formation assumed to involve alterations in RBC membrane skeleton

- the predominant shape in hereditary elliptocytosis

- diseases → hereditary elliptocytosis, iron deficiency anemia, thalassemia, anemia associated with leukemia

what is a keratocyte (helmet cell)?

has a concavity on one side and two hornlike protrusions on either end and produced by impalement on a fibrin strand

- two halves of the RBC hang over the strand, membranes touch and fuse, produces a vacuole-like inclusion on one side called a blister cell, and the vacuole bursts which leaves a notch with two spicules

-diseases → microangiopathic hemolytic anemias, glomerulonephritis, Heinz-body hemolytic anemia, heart-valve hemolysis

what is a knizocyte?

cells with more than two concavities (double stoma)

- most have a dark-staining band across the center with pale area on either side and surrounded by a rim of pink-staining Hb

- mechanism of formation is unknown

what is a leptocyte?

thin, flat cells with normal or larger than normal diameter

- MCV is usually decreased with an increased surface-to-volume ratio (due to decreased Hb content or increased surface area)

- usually cup shaped like a stomatocyte (cup has little depth)

- target cells can be formed from leptocytes on dried blood smears

- diseases → thalassemia, iron deficiency anemia, hemoglobinopathies, liver disease

what is a schistocyte (RBC fragment)?

caused by mechanical damage to cells and has a variety of shapes (triangular, comma shaped, helmet shaped, and usually microcytic)

- normal deformability but reduced survival

- fragments can assume a spherical shape… may hemolyze or be removed by spleen

- diseases → microangiopathic hemolytic anemias, DIC, severe burns, uremia, heart-valve hemolysis

what is a spherocyte?

RBCs that have lost their biconcavity due to decreased surface-to-volume ratio… densely stained sphere lacking central pallor

- often appear microcytic but MCV is usually normal

- the only RBC that can be called hyperchromic because of increased MCHC

- diseases → hereditary spherocytosis, severe burns, transfusion with ABO incompatibility, Heinz-body hemolytic anemias

what is a stomatocyte (mouth cell)?

RBCs that have a slit-like area of pallor and is a reversible shape

- wet-prep appears as cup-shaped discs

- thought to be the result of an increase in the lipid content or area of the inner leaflet

- can appear as artifact on smear which means care should be taken when calling stomatocytes

- diseases → hereditary stomatocytosis, lead intoxication, alcoholic cirrhosis, spherocytosis

what is hyperchromic?

contains more Hb than normal and the only RBC that should be hyperchromic is the spherocyte meaning the term should be used sparingly (if ever)

what is hypochromia?

RBCs contain less Hb than normal and MCHC will be decreased with a central pallor >1/3 of the diameter of the RBC… result of decreased or impaired Hb synthesis

what are polychromatophilic RBCs (reticulocytes)?

usually larger than normal RBCs and has a bluish tinge on a Romanowsky stain due to residual RNA in the cytoplasm (must use a supravital stain to definitively identify reticulocytes)

- larger numbers are associated with an erythroid hyperplastic marrow due to decreased RBC survival and hemorrhage

what is basophilic stippling? (RBC inclusions)

bluish-black granular (vary in size and distribution) inclusions that is distributed across the entire cell area and composed of aggregated ribosomes

- believed that stippling is produced during slide prep as artifact (not seen in living cells)

- can occur when slide is dried slowly or stained rapidly

- seen in lead poisoning, anemia associated with abnormal Hb synthesis, thalassemia

what are cabot rings? (RBC inclusions)

reddish violet RBC inclusions in the formation of a figure 8 or oval ring

- thought to be remnants of spindle fibers from mitosis

- seen in severe anemias and dyserthropoiesis

what are howell-jolly bodies? (RBC inclusions)

dark purple or violet spherical granules and are nuclear (DNA) fragments

- usually occur singly in RBCs, rarely more than two per cell

- associated with nuclear maturation abnormalities

- seen in post-splenectomy, megaloblastic anemias, some hemolytic anemias, functional asplenia, severe anemia

what are heinz bodies? (RBC inclusions)

appears as 2-3 μm round masses lying just under or attached to the cell membrane when stained with supravital stain and composed of aggregated denatured Hb

- do not stain with romanowsky stain

- seen in G6PD deficiency, unstable Hb disorders, oxidizing drugs or toxins, post-splenectomy

what are pappenheimer bodies? (RBC inclusions)

damaged secondary lysosomes and mitochondria variable in their composition of protein and iron and appears as clusters of small granules in RBCs and erythroblasts

- romanowsky stains protein matrix of granules and prussian blue stains iron portion

- only occurs in pathological states (sideroblastic anemia, thalassemia)

what are sideroblasts? (RBC inclusions)

nucleated RBCs that contain stainable iron granules

what are siderocytes? (RBC inclusions)

non-nucleated mature RBCs that contain stainable iron granules

what stain stains siderocytes and sideroblasts?

stained by prussian blue and stains the iron that aggregates blue

- 20-60% all erythroblasts in BM contain iron (increased or decreased in pathologic states)

- reticulocytes and RBCs don’t normally contain stainable iron aggregates unless patient is splenectomized

what are the CBC variations in newborns?

- WBC count is higher (25.0 × 10³/mcL), granulocytes increase but drops within 72 hours

- immature WBCs in circulation for 2 weeks

- RBCs are macrocytic (large)

- reticulocyte count is 2-6%

- at birth, highest RBC, Hb, Hct values then gradually decreases (MCV neonates 108 fL, decreased to 77 fL between 6 months to 2 years, MCHC remains constant)

what are the CBC variations in children?

- lymphs are predominant cell until ages 4 or 5

- 4-5 years, there is an equal number of lymphocytes and granulocytes

- 8 years old, same WBC subsets as adults (1.8 - 7.0 × 10³/mcL)

what are the CBC variations in the elderly?

- BM cellularity decreases with age

- anemia becomes more prevalent due to iron deficiency, vitamin B₁₂ deficiency, anemia of chronic inflammation, kidney disease, and decreases testosterone levels

- malignancies occur at higher incidence

what are the CBC variations in African Americans?

- lower Hb, Hct, MCV than caucasians

- 30% prevalence of alpha-thalassemia

- WBCs lower, particularly granulocytes but lymphocytes are higher