Abnormal Erythrocytes
Bite Cells (arrowed) |
- Hypochromic
microcytic erythrocytes:
occur in certain types of anaemia including iron deficiency anaemia and
thallasaemia. They are smaller than normal erythrocytes, usually <6
micrometers diameter.
- Macrocytes
are
larger than normal erythrocytes occurring in certain types of anaemia
including those caused by B12 or folate deficiency (and others listed here).
- Normoblasts
(or erythroblasts):
are the immediate precursors of erythrocytes - at this stage the
nucleus is retained as can be seen in the illustration. There are four stages of
development.
- Spherocytes:
are
red cells with a loss of membrane leading to reduced diameter and
decreased surface area but normal volume. They are seen in hereditary
spherocytosis, erythroblastosis fetalis and acquired hemolytic
anemias.
- Stomatocytes:
erythrocytes with a loosely folded, mouth-like pale area across the
cell. They are seen in hereditary stomatocytosis, lead poisoning and
thalassemia trait.
- Target cells
(or codocytes):
have the hemoglobin concentrated in the middle and the periphery of the
cell, and thereby resemble targets. They can be seen in
hemoglobinopathies, e.g. thalassemias, and iron deficiency anemia.
- Teardrop
erythrocytes (or dacryocytes):
are seen when there is extramedullary erythropoiesis or with marrow
disorders or marrow infiltration, such as myelofibrosis or metastatic
carcinoma
- Elliptocytes:
occur
with several inherited disorders predisposing to haemolytic anaemia
They can also be seen in acquired disorders, such as iron defiency
anemia, infectious anemias, thalassemia, and in newborn babies.
- Sickle cells: are seen in sickle cell anaemia
- an autosomally inherited disorder.
- Acanthocytes:
are spherocytical cells with large irregularly placed protrusions.
- Echinocytes:
are red blood cells distorted by exposure to a hypertonic medium.
- Schizocytes
(schistocytes or helmet cells):
are fragmented cells showing bizarre poikilocytosis. They can be seen
in various forms of microangiopathic haemolytic anemia as well as after
injury by mechanical means, e.g. through cardiac valve prostheses.
- Bite
cells: are
indicative of some haemolytic anaemias (e.g. G6DP deficiency). They
occur when there is a precipitation of haemoglobin against a portion of
the inner membrane (known as a Heinz Body). This is later removed in
the spleen leaving a 'bite mark'. Other causes of Heinz bodies (and
thus Bite cells) are oxidant drugs and haemolytic anemia associated
with severe liver disease. Not all bite cells are as evenly shaped as
shown in the top pic - see separate illustration)
- Howell-Jolly
bodies:
are the small dark bodies in the illustration. They are nuclear
remnants which are present in some normal red cells in the bone marrow
but are removed by the spleen during the first few hours the cells
spend in the circulatation. This appearance results from absence of
splenic function, either following splenectomy, or occasionally due to
splenic atrophy.
- Basophilic stippling: of
erythrocytes occurs with lead poisoning or megaloblastic anaemia.
In this latter case the erythrocytes may be nucleated. Other causes here.
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