Sickle Cell Anaemia

By: Ashleigh Robertson, Shannah del Rosario and Sharon Qiao (Xiaoxi)

LSB555: Principles and Practice of Clinical Haematology

Case Study

A young 6 year old girl presented to ED with fever, tiredness, pallor and acute episodes of pain
Clinical examination:
- Icteric sclera
- Splenomegaly
- hand-foot syndrome (pain and swelling of fingers and toes)
Family immigrated from Nigeria 3 years ago

Empirical Dx: Sickle Cell Anaemia

Tests Requested: FBE and other relevant tests

What is Sickle Cell Anaemia?

Sickle cell anaemia is a haemoglobinopathy affecting normal haemoglobin production
Forms distinct sickle red blood cells

Genetics of Sickle Cell Disease

Sickle cell disease is autosomal recessive
25% chance of producing offspring with homozygous sickle cell disease - symptomatic phenotype
50% chance of passing down sickle cell trait genotype [1]

Source: CDC Website [2]

What mutation causes Sickle Cell Disease?

HbA (normal Hb)

HbS

(Sickle cell Hb)

Source: BBC Website [3]

How does sickling occur?

• Glutamic acid has a net charge of -1 (polar)

• Polar glutamic acid would normally bind water molecules – soluble in cytosol

• Valine has a net charge of 0 (non-polar)

• Non-polar valine is hydrophobic [1]

Source: American Society of Hematology [4]

How does sickling occur?

• Valine searches for hydrophobic niche to bind

• Oxygenated HbS has no hydrophobic niche – freely soluble

• Deoxygenated HbS creates hydrophobic pocket for valine from adjacent Hb to bind [1]

Source: New England Journal of Medicine [5]

How does sickling occur?

• HbS molecules polymerise when deoxygenated

• Forming long, rigid fibres

• Sickling reversible by oxygenation of HbS molecules

• Extensive membrane damage can cause irreversible sickle cell formation [2]

Source: New England Journal of Medicine [5]

Sickling manifestations

Chronic Haemolytic Anaemia
Microvascular occlusion
Tissue damage

Chronic Haemolytic Anaemia

• Sickle cells are fragile and more prone to haemolysis – shortened RBC lifespan

• Haemolysis of RBCs cause anaemia and hyperbilirubinaemia [6]

Empirical Dx:

Jaundice in sclera - hyperbilirubinaemia

Fatigue and pallor - haemolytic anaemia

Microvascular occlusion

• Occurs due to blockage of small vasculature by sickle cells

• Hypoxic injury to these vessels cause pain crisis

• Commonly occurs in the bones of the hands and feet

• Adhesion of sickle cells to endothelium promotes occlusion [6]

Empirical Dx:

Hand-Foot Syndrome - vaso-occlusive crises

Recurring episodes of acute pain - occlusion of microvasculature

Tissue damage

• Sickle cells commonly get trapped in the spleen

• Can lead to splenic infarction, fibrosis, and progressive shrinkage – decreasing the functionality of the spleen

• Sickle cells can also cause infarctions in other tissues – causing organ failure [6]

Empirical Dx:

Splenomegaly - continuous screening and removal of sickle cells (Autosplenectomy)

Prevalence of Sickle Cell Anaemia

• Sickle Cell Anaemia is frequently found in West and Central Africa, as well as the Middle East and India [7]

Source: Encylopaedia Britannica Inc. [7]

Occurrence of sickle cell anaemia parallels the incidence of endemic malaria – suggests protective adaptation with resistance against malaria parasite [7]

Source: Encylopaedia Britannica Inc. [7]

Diagnosis of Sickle Cell Anaemia

Morphology on Peripheral Blood Smear

Peripheral Blood Smear [8]

Howell Jolly Bodies [10]

Sickle cell [8]

Target Cell [8]

Hypochromic Cell [9]

Polychromatic Cell [8]

Red Cell Fragment (Schistocyte) [11]

Full Blood Examination

   Patient Dx:

```
Hb - Decreased 
```
```
RCC - Decreased
```
```
Hct - Decreased
```
```
MCV - Normal
```
```
MCH - Normal
```
```
MCHC - Normal
```
```
RDW - Increased
```
```
WCC - Increased 
```
```
PLT - Increased 
```

Source: [12],[13],[14]

Haemoglobin Electrophoresis

Source: American Society of Hematology [15]

Haemoglobin Electrophoresis

Source: Helena Laboratories [16]

High Performance Liquid Chromatography (HPLC)

Source: Universite Libre de Bruxelles [17]

Isoelectric Focusing (IEF)

Source: Universite Libre de Bruxelles [17]

Sickle Solubility Test - Sickledex

Source: Streck [18]

Negative

Positive

Treatment of Sickle Cell Anaemia

Treatment

Blood and Bone Marrow Transplantation
Hydroxyurea
Treatment of complications

Blood and Bone Marrow Stem Cell Transplantation

Sickle cell anaemia has no universal cure yet
A small number of people are cured by blood and bone marrow transplants [19]
Transplant aims to replace defective stem cells with normally functioning ones
Normal function? Reject reaction?

Before and after procedure:

```
HLA tissue typing
```
```
Chemotherapy
```

Side effect:

```
Infection
```
```
Graft-vs-Host Disease
```
```
Graft Failure
```

What's Next?

Slow recovery [19]
- Takes 6-12 months to recover normal RBC levels and immune function
- Monitor risk of infection
- Some patients may need regular blood transfusion

Patient Rx:

```
Routine health care every 6 months
```
```
Eye check up
```
```
Ultrasound scan of brain
```
```
Penicillin and Folate acid
```

Parental education: learn to manage symptoms

```
Genetic counselling
```

Hydroxyurea

For severe sickle cell anaemia [19]
Increases production of Foetal Haemoglobin (HbF)
Prevents RBC from sickling
Improve anaemia
Reduces painful sensation from sickle cell crises
Reduces chances of blocking small vessels
Reduces visits to hospital

Hydroxyurea will manage patient's:
Fatigue and Pallor
Recurrent pain crises
Hand-Foot Syndrome

Management of complications

Source: National Institute of Health [19]

Any Questions?

References

[1] Keohane EM, Smith LJ, Walenga JM. Rodak’s Hematology: Clinical Principles and Application. 5th Edition. Elsevier Inc: 2012. Chapter 27, Hemoglobinopathies (Structural Defects in Hemoglobin); p. 431-6.

[2] CDC: Centers for Disease Control and Prevention. Sickle cell trait [Internet]. 2013 [cited 2015 Apr 24]. Available from: http://www.cdc.gov/ncbddd/sicklecell/traits.html

[3] BBC. Gene mutations [Internet]. 2014 [cited 2015 Apr 24]. Available from: http://www.bbc.co.uk/bitesize/higher/biology/genetics_adaptation/mutations/revision/1/

[4] Schechter A. Hemoglobin research and origins of molecular medicine [Internet]. American Society of Hematology. 2008 [cited 2015 Apr 24]. Available from: http://www.bloodjournal.org/content/112/10/3927?sso-checked=true

[5] Bunn FH. Pathogenesis and Treatment of Sickle Cell Disease. The New England Journal of Medicine, Vol 337. 1997 [cited 2015 Apr 24].

[6] Kumar V, Abbas AK, Fausto N, Aster JC. Robbins and Cotran: Pathologic Basis of Disease. 8th edition. Elsevier Inc: 2010. Chapter 14, Anemias.

[7] Encyclopaedia Britannica Online. “Malaria and sickle cell anemia, distribution of” Map [Internet]. [cited 2015 Apr 24]. Available from: http://www.britannica.com/Ebchecked/topic/556001/South-Asia/images-videos/160694/malaria-and-sickle-cell-anemia-distribution-of

[8] Chambers K. Blood smears from patients with sickle cell disease – part 3 [internet] Leicester, UK: De Montfort University; August 23, 2011 [cited 2015, April 26] available from: http://www.sicklecellanaemia.org/OER/article.php?id=68

[9] Maslak P. Hypochromic erythrocytes – 1 [internet] Washinton DC, USA: American Society of Hematology (ASH) ; March 04, 2009 [cited 2015, April 27] available from: http://imagebank.hematology.org/AssetDetail.aspx?AssetID=3901

[10] Maslak P. Howell-Jolly bodies– 1 [internet] Washinton DC, USA: American Society of Hematology (ASH) ; January 10, 2008 [cited 2015, April 27] available from: http://imagebank.hematology.org/AssetDetail.aspx?AssetID=3677

[11] Maslak P. Schistocytes – 1 [internet] Washinton DC, USA: American Society of Hematology (ASH) ; January 10, 2008 [cited 2015, April 27] available from http://imagebank.hematology.org/AssetDetail.aspx?AssetID=3718&AssetType=Asset

[12] Valavi E, Ansari, M-J A, Zandian K, How to Reach Rapid Diagnosis in Sickle cell Disease? [internet] Iran J Pediatr, vol 20 (no 1) 69-74, March 2010 [cited 2015, April 28] available from www.bioline.org.br/pdf?pe10009

[13] Thame M, Grandison Y, Mason K, Thompson M, Higgs D, Morris J, Serjeant B, Serjeant G. The Red Cell Distribution Width in Sickle Cell Disease – is it of Clinical Value? [internet] Clinical and Laboratory Hematology volume 13 [p 229-237] September 1991 [cited 2015, April 26] available from: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2257.1991.tb00277.x/abstract

[14] Lichtin AE, Sickle Cell Disease [internet] Merck Manual, October 2013 [cited 2015, April 26] available from: www.merckmanuals.com/professional/hematology-and-oncology/anemias-caused-by-hemolysis/sickle-cell-disease

[15] Kuo K. Case Study: A 12-Year-Old Boy With Normocytic Anemia and Bone Pain [internet] American Society of Hematology (ASH) ©2015 [cited 2015, April 27] available from: http://www.hematology.org/Fellows/Case-Studies/725.aspx

[16] Helena Laboratories: Haemoglobin Electrophoresis Procedure [internet] Beaumont, Texas: Helena Laboratories [date unknown] [cited 2015, April 20] available from: http://www.helena.com/Procedures/Pro015%20Rev6.pdf

[17] Diagnosis, last updated 2001, August 16. [cited 2015, April 25] available from: http://erasmeinfo.ulb.ac.be/globule/English/sickle_diag.htm

[18] Streck, Sickledex [internet] Omaha, USA [date unknown] [cited 2015, April 27] available from: http://www.indianablood.org/lab-services/DonorTestingLab/Documents/Package%20Inserts-Donor%20Testing/Donor%20Tesing_Uploaded_8-22-2013/SICKLEDEX%20for%20Hgb-S.pdf

[19] National Institutes of Health, D.o.H.a.H.S., How Is Sickle Cell Anemia Treated. September 28, 2012.