A Case of Anaemia

Lent term year 1

The case

• 21 year old Afro-Caribbean man

• Admitted with abdominal pain and priapism

Priapus: son of Aphrodite

Why does this occur?

Sickle Cell Disease• Sickle cell disease is a common haemolytic

disorder in black races.• It is due to the presence of HbS, caused by a

single base mutation from adenine to thymine. This produces a substitution of valine for glutamine at the 6th codon of the -globin chain.

• In the homozygous state both -chains are abnormal, whereas in the heterozygous state only one chromosome is abnormal, and the disease is much less severe. HbF is normal.

Haemoglobin

• Normal adult Hb (HbA) consists of 2 and 2 polypeptide globin chains. These fold in a quaternary structure to enfold a haem group. Hb S is less soluble than Hb A and, when deoxygenated, undergoes polymerisation, leading to the formation of sickle shaped cells.

What is the cause of his symptoms?

Symptoms in Sickle cell disease:• Vascular occlusion due to sickle cells lodging in

capillaries. This can occur in any part of the body, causing a “sickle crisis”.

• Typically these can cause bone pain, pleuritic pain, cerebral infarcts, priapism and hepatic pain with fever.

• Long term complications can occur, including susceptibility to strp. Pneumoniae infection, chronic leg ulcers, aseptic necrosis of bone, blindness and chronic renal disease. Gallstones occur from pigment due to persistent haemolysis.

Sickle cells block the capillaries

Also:

• A normal blood cell lives for around 120 days

• Sickle cells do not live as long, and break up more easily (Haemolysis)

• This leads to a chronic state of anaemia

What investigations would you arrange?

Investigations• A full blood count: Hb 6-8g/dl with high

reticulocyte count.• Blood film: Sickling of rbcs induced by

sodium metabisulphite. Sickledex is a commercial test where sodium dithionite gives a turbid appearance to HbS, wheras normal Hb remains clear.

• Hb electrophoresis. No HbA, 80-95% Hb SS, 2-20% HbF

Sickle cell testing

electrophoresis

What is the immediate treatment?

treatment

• Maintain hydration with IV fluids,

• oxygen via face mask

• analgesia, usually with opiates.

• Consider underlying cause, such as sepsis.

• Priapism may be treated with normal saline washouts of corpora cavernosa and direct injection with adrenergic agent, such as methoxamine or phenylephrine (unlicenced).

What about other causes of anaemia??

Classification of anaemia:1. Haemolytic- blood cells breaking up

2. Aplastic- blood cells not being made

3. Blood loss

Haemolytic Disease: congenital• Sickle cell: may get sickle “Trait” of

heterozygous form. OK unless stressed in oxygen requirements e.g scuba diving, GA

• Spherocytosis: autosomal dominant

• G6PD deficiency (fava beans)

Haemolytic disease: acquired• Haemolytic disease of newborn (Rhesus

disease)

• Drug-induced e.g penicillin, quinine

• Autoimmune

• Infection e.g malaria

• Alloimmune: blood transfusion reactions

Aplastic anaemia: failure of bone marrow