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Sickle Syndromes

Title               

Ñ    Sickle Syndromes

Definition

Ñ    Homozygotes;

Sickle cell anaemia

Ñ    Heterozygotes:

Sickle cell trait

Aetiology

Ñ    Single-base mutation in beta-globin chain

 

 

Sickle Cell Anaemia

Title               

Ñ    Sickle Cell Anaemia

Definition

Ñ    A hereditary haemoglobinopathy resulting from a point mutation of the globin gene

Pathogenesis

Ñ    Deoxygenated Hb S molecules become insoluble and polymerise

Ñ    This results in decreased flexibility of the red cell, which becomes rigid and sickle shaped

Sickling results in:

Ñ    Shortened survival of the red cell

Ñ    Obstruction of small vessels and infarction

Clinical Features

History

Ñ    May present in childhood or adult life

RS

Ñ    Chest pain

GIT

Ñ    Abdominal pain

Ñ    Abnormal liver function tests

KUS

Ñ    Haematuria:

Papillary necrosis

Ñ    Lack of concentration of urine:

Renal tubular defects

RAG

Ñ    Priapism

Due to vaso-occlusion

CNS

Ñ    Fits

LMS

Ñ    Bone pain

Examination

IS

Ñ    Leg ulcers

HS

Ñ    Anaemia

IS

Ñ    Jaundice

GIT

Ñ    Hepatomegaly and liver dysfunction:

Due to trapping of sickle cells

CNS

Ñ    Hemiparesis

LMS

Ñ    Digits of varying lengths:

Following bone infarcts

Complications

RS

Ñ    Acute sickle chest syndrome:

Dyspnoea, chest pain, hypoxia and chest x-ray changes (consolidation)

Causes:

·          Infection

·          Fat embolism from necrotic bone

·          Pulmonary infarction

GIT

Ñ    Gallstones

KUS

Ñ    Chronic renal failure

HS

Ñ    Hyposplenism:

Due to multiple splenic infarcts

Ñ    Marrow aplasia:

Following viral infections especially parvovirus

Ñ    Acute sequestration in liver and spleen:

·          Painful enlargement of the spleen:

Acute onset

·          Splenic pooling of red cells

·          Sometimes with circulatory collapse

·          Occurs in childhood before splenic infarctions result in hyposplenism

Ñ    Haemolysis:

Drugs, infection, associated G6PD deficiency

CNS

Ñ    Blindness:

Retinal detachment, proliferative retinopathy

Ñ    Meningitis:

Streptococcus pneumoniae

LMS

Ñ    Aseptic necrosis of bone

Ñ    Osteomyelitis:

Salmonella

Investigations

Fluids

Blood

Haematology

Ñ    Anaemia

Ñ    Reticulocyte count:

High

Ñ    Blood film:

·          Features of hyposplenism:

Multiple splenic infarctions lead to a fibrotic non-functioning spleen

Ñ    Sickling Test:

Sickling induced by sodium metabisulphite

Ñ    Sickle solubility test:

Hb S and sodium dithionite (reducing solution) gives a turbid solution

Normal Hb and sodium dithionite gives a clear solution

Biochemistry

Ñ    HB electrophoresis:

No Hb A

Hb SS 80-95%

Hb F 2-20%

Management

Control

Drugs

Ñ    Acute attacks:

Fluids, oxygen, antibiotics, analgesia

Ñ    Hydroxycarbamide:

Increases Hb F concentration

Reduction of neutrophils may also help

Ñ    Inhaled nitric oxide:

Reduces vascular adhesion of red cells

Inhibits platelet function

Vasodilator

Biological Agents

Ñ    Blood Transfusion:

·          Correct anaemia

·          Suppress production of Hb S:

Repeated crises

Before elective surgery

During pregnancy

Ñ    Exchange transfusion:

Severe crises

Recurrent crises

Before emergency surgery

Ñ    Bone marrow transplantation

Prevention

Drugs

Ñ    Penicillin:

Hyposplenism

Biological agents

Ñ    Immunisation:

Pneumococcus

Haemophilus influenza type B

Prognosis

Ñ    Marked variation

Ñ    Some die in early life

Ñ    Others relatively normal life span

 

 

Sickle Cell Trait

Title

Ñ    Sickle cell trait

Clinical Features

Ñ    No symptoms unless anoxia supervenes or during anaesthesia

Investigations

Fluids

Blood

Ñ    Sickle test

Ñ    Hb electrophoresis

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