The document provides an overview of red blood cell morphology, describing normal red blood cell appearance and abnormalities that may be seen related to size, shape, color, distribution, and inclusions. Key points include that normal red blood cells are biconcave discs that appear reddish at the periphery and pale in the center, and abnormalities may indicate diseases related to plasma proteins, erythropoiesis, hemoglobin formation, cell damage, or increased erythropoiesis. Specific abnormalities described include microcytosis, macrocytosis, hypochromia, poikilocytosis, spherocytes, and inclusions like Howell-Jolly bodies.

1. BLOOD CELL MORPHOLOGY
PRESENTED BY
MISS TASMIA ZEB

2. INTRODUCTION:
• Study of morphology of blood cells in a wellspread and well-stained blood film
yields invaluable diagnostic information. Therefore the blood film should be
examined carefully and systematically. It is preferable that the film should be
mounted with a cover glass using a neutral mounting medium. It provides not
only good refraction but also preserves the blood film. First it should be
examined under low power (x10) objective. This will give an idea of the quality
of film and distribution and staining of cells and platelet aggregates. It also
gives the idea about rouleaux formation, presence of agglutinates, dimorphic
population of cells and presence of some haemoparasites e.g., microfilariae.
Then select a suitable area and switch to dry high power (x40) objective. Oil
immersion (x100) objective should be reserved for the study of finer details of
the cells. There are three types of cells in the blood, RBC, WBC and platelets.
Each of these should be studied systematically.

3. MORPHOLOGY OF RED BLOOD CELLS
• Normal red blood cells appear as circular discs of about 6-8.5 µm in
diameter, roughly equal to the size of nucleus of a small lymphocyte.
They have bright reddish colour (due to haemoglobin) at the
periphery, which becomes pale towards the centre because of the
biconcave shape of RBC.
• The central pale area normally does not exceed one third of the total
area of RBC. In a normal blood film RBC lie separately in the central
area of the film. RBCs are examined for their distribution, size, shape,
colour (Hb content) and inclusions.

4. MORPHOLOGY OF RED BLOOD CELLS
• Abnormalities in these characters may be artefactual or may arise in
disease because of:
1. Changes in plasma proteins and development of antibodies to RBC
surface antigens.
2. Abnormal erythropoiesis
3. Inadequate haemoglobin formation
4. Damage to red cells in circulation
5. Increased erythropoiesis

5. ABNORMALITIES OF DISTRIBUTION
• Rouleaux formation: Rouleaux formation (stacking of RBC on top of each
other) is seen when fibrinogen concentration of blood is increased e.g., in
infections, pregnancy and tissue necrosis. But it is characteristically seen in
conditions with abnormal globulin production e.g., in multiple myeloma. The
degree of rouleaux formation is directly proportional to ESR.
• Agglutination: Agglutination is defined as random aggregation of RBC. These
form clusters of varying number of cells. This results from bridging of cells by
antibody molecules, particularly IgM, against antigens on surface of RBC
circulating in plasma. These may have been produced endogenously
(autoantibodies) as in cold haemagglutinin disease or rarely have been
introduced from out side e.g., infusion of large amounts of mis-matched
plasma. In incompatible blood transfusion agglutinates seen comprise of cells
of donor origin.

6. ABNORMALITIES OF SIZE
• Anisocytosis: If the size of RBC varies, in the same blood film, beyond
normal limits, it is termed anisocytosis. It is expressed as + to +++. It is
a non-specific feature of several haematological disorders.
• Microcytosis: When the average size of RBC in a blood film is less
than normal it is termed microcytosis. The degree of microcytosis is
directly proportional to decrease in MCV. It seldom occurs alone but
is usually accompanied with hypochromia. Microcytosis is commonly
seen in iron deficiency anaemia and thalassaemia. Sometimes small
cells with no central pale area are seen. These usually have normal
MCV. These are termed spherocytes.

7. ABNORMALITIES OF SIZE
• Macrocytosis: When the average size of RBC is more than normal, it is
termed macrocytosis. The degree of macrocytosis is directly
proportional to increase in MCV . Common causes of macrocytosis
are liver disease, megaloblastic anaemia, aplastic anaemia, refractory
anaemia, obstructive airway disease, excess of alcohol, treatment
with hydroxyurea and hyperglycaemia. In patients whose marrow is
responding by increased haematopoiesis and there are lot of
polychromatic cells, these appear as macrocytes.

8. ABNORMALITIES OF COLOUR
• The only true variation in colour is the hypochromia. It results from
decreased haemoglobinisation of RBCs, commonly seen in iron
deficiency anaemia and thalassaemia. Degree of hypochromia is
proportional to MCHC. Leptocytes may appear hypochromic because
of flattening. Spherocytes appear hyperchromic because of loss of
central pale area and increased thickness of the cell. Macrocytes may
also appear hyperchromic because of increased thickness.

9. ABNORMALITIES OF COLOUR
• Target cells: have a central haemoglobinised area, surrounded by a
pale ring and then a peripheral haemoglobinised area. These also
result from increased membrane surface due to increase in its
cholesterol and phospholipid content. These are characteristically
seen in thalassaemias, HbC disease, HbD disease, HbE disease,
obstructive liver disease, postsplenectomy and iron deficiency
anaemia. If an artefact, then these are confined to only a portion of
blood film. Dimorphism: It is the term used when two distinct
populations of RBC are seen in the blood film. One population may be
normal and the other abnormal, particularly hypochromic microcytic
or macrocytic. It is seen in sideroblastic anaemia, when a patient has
been transfused or when a patient is receiving haematinics for
treatment of deficiency anaemia.

10. ABNORMALITIES OF SHAPE
• Poikilocytosis: When the shapes of RBCs vary more than expected in normal
individuals, in the blood film, it is termed poikilocytosis. RBC of abnormal
shape is termed a poikilocyte. Poikilocytosis is also a non-specific feature seen
in several haematological disorders, abnormal erythropoiesis, megaloblastic
anaemia, MDS, iron deficiency anaemia, thalassaemia, and myelofibrosis.
However specific types of poikilocytes are diagnostic of specific disorders.
• Spherocytes: When RBCs are more spheroidal than normal, these are termed
spherocyte. These may result from genetic defects of red cell membrane as in
hereditary spherocytosis, because of interaction between Ig or complement
coated red cells with macrophages as in immune haemolytic anaemias, ABO
haemolytic disease of newborn and from action of certain bacterial toxins
e.g., Cl.perfringens. Spherical forms may be seen when anticoagulated blood
is allowed to stand for a long time e.g., banked blood.

11. ABNORMALITIES OF SHAPE
• Elliptocytes and Ovalocytes: About 10% RBC in a normal blood film,
particularly at the tail end, appear oval and less commonly elliptical in shape.
Their proportion is higher in iron deficiency anaemia, megaloblastic anaemia
and myelofibrosis. In iron deficiency these are usually more elongated (pencil
cells), whereas in megaloblastic anaemia these are macrocytic as well (oval
macrocytes).In myelofibrosis ovalocytes are somewhat pointed on narrow
side (tear drop cells). If this shape is seen in vast majority of cells and in
central area of the film then the condition is termed Elliptocytosis or
Ovalocytosis. This results from a hereditary membrane defect.
• Stomatocytes: When RBCs have a 'mouth' like slit, these are called
stomatocytes. Few stomatocytes are usually seen in normal blood film. Their
number is increased in alcoholism, liver disease and Rh null disease. These are
numerous in a hereditary membrane defect.

12. ABNORMALITIES OF SHAPE
• Schistocytes: These are fragmented red blood cells of various shapes and
sizes. Large cells from which portions are fragmented some times appear as
helmets and are called helmet cells. Schistocytes are increased in conditions
like iron deficiency anaemia, megaloblastic anaemia and thalassaemia but are
characteristically increased when RBCs are exposed to mechanical trauma.
This occurs when RBCs are passing through meshes of fibrin as in DIC, or
through narrowed vessels as in microangiopathy or through prosthesis.
• Echinocytes and Burr cells: Echinocytes or crenated cells have evenly
distributed blunt spicules of uniform size on their surface. These are formed if
anticoagulated blood is allowed to stand for long periods e.g., over night at
room temperature or if the film is prepared on a slide that has fatty material
on it or if pH of the blood is raised.These are also seen in patients who have
uraemia or have been on cardiopulmonary bypass. Burr cells are also
echinocytes but their spicules are reversible

13. ABNORMALITIES OF SHAPE
• Acanthocytes: These are small densely staining RBC with thorn like
projections. Generally the projections are fewer, of varying sizes,
variable number and more blunted than echinocytes. These may be
hereditary or acquired. Hereditary causes include McLeod phenotype
and disorders of lipid metabolism. The acquired causes include spur
cell anaemia and chronic liver disease.
• Pyropoikilocytes: These are seen in a rare hereditary disorder,
pyropoikilocytosis, and comprise microspherocytes and fragments of
RBC. Their number greatly increases when blood is heated to 45°C.
• Sickle cells: These are thin, elongated, deeply staining red cells with
elongated ends. These may be straight, curved or of various other
shapes. These are produced by polymerisation of HbS in sickle cell
disease.

14. INCLUSIONS IN RBC
• Hb crystals: Some abnormal Hb, particularly C and S polymerise to form crystals inside RBC.
Polymerisation of HbS gives a distinct shape to RBC, sickle cell. HbS and HbC occurring together
polymerise to form straight crystals with parallel sides and one blunt projecting end or multiple
crystals projecting from a common centre. HbC crystals are hexagonal with blunt ends.
• Howell-Jolly bodies: These are small rounded fragments of the nucleus staining reddish-blue to
blue-black resulting from incomplete extrusion of the nucleus. These contain DNA and are <1 µm
in diameter. These usually occur singly in RBC but may be multiple. Most common cause is
splenectomy or splenic atrophy but these are also seen in alcoholism, sickle cell anaemia, and
megaloblastic anaemia.
• Basophilic stippling or punctate basophilia: These are fine to coarse, deep blue to purple, small
but multiple inclusions of varying sizes. These represent aggregated ribosomes. These are seen in
thalassaemia, megaloblastic anaemia, liver disease, lead poisoning, unstable Hb, pyrimidine
5nucleotidase deficiency and infections.

15. INCLUSIONS IN RBC
• Pappenheimer bodies: These are small, dark staining, irregular
granules composed of haemosiderin occurring near the periphery of
the cells. Their presence is related to iron overload. These stain
positively with perl’s stain. These are seen in sideroblastic anaemia,
dyserythropoietic anaemia and thalassaemia.
• Cabot rings: This is thin reddish blue, ring like structure occupying
varying portion of RBC. It may be twisted to form figure of 8. Its origin
is not clear. These are commonly seen in severe anaemia of any type
but most commonly in megaloblastic anaemia, lead poisoning and
dyserythropoietic anaemias. These may occur alone but are usually
associated with punctate basophilia and Howell-Jolly bodies.
• Parasites: These include malarial parasites and Babesia.