[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Red cells and bleeding disorders](https://durgical.com/en/general-pathology/areas/red-cells/) › Red cell morphology on the smear

# Red cell morphology on the smear

- Topic

Red cell shapes and inclusions are clues: each abnormal form points to a small set of diseases.

Updated Nov 12, 2026

## Key points

- Spherocytes: hereditary spherocytosis and warm autoimmune haemolysis.
- Schistocytes (helmet cells, fragments): TTP, HUS, DIC, malignant hypertension, mechanical valves.
- Target cells: thalassaemia, haemoglobin C, liver disease, asplenia.
- Howell–Jolly bodies: nuclear remnants in asplenia; basophilic stippling: lead poisoning and thalassaemia.
- Heinz bodies (supravital stain) and bite cells: oxidant haemolysis, G6PD deficiency.

## What it is

A normal red cell is a biconcave disc with central pallor about a third of its diameter. Damage to the membrane, the haemoglobin, the marrow or the spleen changes the shape or leaves inclusions. Reading the smear turns these shapes into a short differential diagnosis and often points to the mechanism: membrane loss (spherocytes), mechanical cutting (schistocytes), excess membrane (target cells), polymerized haemoglobin (sickle cells), squeezing through a fibrotic marrow (teardrops) or splenic removal of inclusions (bite cells).

## Abnormal red cells and what they suggest

| Cell | What it looks like | Mechanism | Main causes |
| --- | --- | --- | --- |
| [Spherocyte](https://durgical.com/en/conditions/hereditary-spherocytosis/) | Small, dense, no central pallor | Loss of membrane | Hereditary spherocytosis, warm autoimmune haemolysis |
| [Schistocyte](https://durgical.com/en/conditions/thrombotic-thrombocytopenic-purpura/) | Fragments, helmets, triangles | Cut by fibrin strands or turbulence | TTP, HUS, DIC, mechanical valves |
| [Target cell](https://durgical.com/en/conditions/thalassemias/) | Central dark spot inside pallor | Excess membrane relative to haemoglobin | Thalassaemia, haemoglobin C, liver disease, asplenia |
| [Sickle cell](https://durgical.com/en/conditions/sickle-cell-disease/) | Crescent or holly-leaf shape | Polymerized deoxygenated HbS | Sickle cell disease |
| [Teardrop cell (dacrocyte)](https://durgical.com/en/conditions/essential-thrombocythaemia-and-primary-myelofibrosis/) | Single tapered tail | Deformed leaving a fibrotic or infiltrated marrow | Myelofibrosis, metastatic cancer in marrow |
| [Bite cell](https://durgical.com/en/conditions/glucose-6-phosphate-dehydrogenase-deficiency/) | Bite-shaped notch | Splenic removal of Heinz bodies | G6PD deficiency, oxidant drugs |
| [Howell–Jolly body](https://durgical.com/en/conditions/asplenia-and-hyposplenism/) | Small round dark dot | Nuclear remnant not removed by the spleen | Asplenia, sickle cell disease |
| [Basophilic stippling](https://durgical.com/en/conditions/lead-poisoning/) | Fine blue dots | Persisting ribosomal RNA | Lead poisoning, thalassaemia |
| [Pencil cell](https://durgical.com/en/conditions/iron-deficiency-anaemia/) | Long thin elliptical cell | Iron-deficient erythropoiesis | Iron deficiency anaemia |

## Clinical notes

- Schistocytes with thrombocytopenia are an emergency clue to thrombotic microangiopathy.
- Rouleaux (stacked coins) suggest high immunoglobulin levels such as myeloma.

## In the lab

- Automated analysers give size and colour; only the smear shows shape and inclusions.
- Supravital stains show reticulocytes and Heinz bodies; Prussian blue shows siderocytes and ring sideroblasts.

## Memory aid

Spheres lost membrane, targets have too much, schistocytes were cut, teardrops were squeezed, bites were plucked.

## Test yourself

Think of the answer, then tap the question to see it.

## Which red cell finding indicates a missing or nonfunctioning spleen?

Howell–Jolly bodies (nuclear remnants), often with target cells.

## What produces bite cells?

Splenic macrophages remove Heinz bodies (denatured haemoglobin) from oxidant-damaged red cells, as in G6PD deficiency.

## Which disorders give schistocytes?

Microangiopathic haemolysis (TTP, HUS, DIC, malignant hypertension) and mechanical heart valves.

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## Elsewhere in DurgiPedia

- [Blood cells on a smear: erythrocytes, leukocytes, platelets](https://durgical.com/en/histology/blood-cells-on-a-smear-erythrocytes-leukocytes-platelets/)

## Connections

## Related 4

- [Anaemia: classification](https://durgical.com/en/general-pathology/anaemia-classification/)
- [Haemolysis: extravascular vs intravascular](https://durgical.com/en/general-pathology/haemolysis-extravascular-vs-intravascular/)
- [Traumatic haemolysis](https://durgical.com/en/general-pathology/traumatic-haemolysis/)
- [Essential thrombocythaemia and primary myelofibrosis](https://durgical.com/en/general-pathology/essential-thrombocythaemia-and-primary-myelofibrosis/)

## Related conditions 10

- [Hereditary spherocytosis](https://durgical.com/en/conditions/hereditary-spherocytosis/)
- [Sickle cell disease](https://durgical.com/en/conditions/sickle-cell-disease/)
- [Thalassemias (α and β)](https://durgical.com/en/conditions/thalassemias/)
- [Glucose-6-phosphate dehydrogenase (G6PD) deficiency](https://durgical.com/en/conditions/glucose-6-phosphate-dehydrogenase-deficiency/)
- [Lead poisoning](https://durgical.com/en/conditions/lead-poisoning/)
- [Asplenia and hyposplenism](https://durgical.com/en/conditions/asplenia-and-hyposplenism/)
- [Thrombotic thrombocytopenic purpura](https://durgical.com/en/conditions/thrombotic-thrombocytopenic-purpura/)
- [Essential thrombocythaemia and primary myelofibrosis](https://durgical.com/en/conditions/essential-thrombocythaemia-and-primary-myelofibrosis/)
- [Megaloblastic anaemia (B12 or folate deficiency)](https://durgical.com/en/conditions/megaloblastic-anaemia/)
- [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Hemolytic anemia: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000571.htm) (MedlinePlus, US National Library of Medicine, 2026); [Anemia | MedlinePlus](https://medlineplus.gov/anemia.html) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/red-cell-morphology-on-the-smear/