Define G6PD Deficiency. Describe its clinical features, investigations, pathophysiology and management.

Definition

• Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked enzyme disorder (affecting males) that leaves red cells vulnerable to oxidative stress, causing episodic acute haemolysis.
• It is the commonest human enzyme defect.

Precipitants (oxidative Triggers)

• Infections (the commonest trigger).
• Drugs — antimalarials (primaquine), sulfonamides, nitrofurantoin, dapsone.
• Fava beans (favism); naphthalene (mothballs).

Clinical Features

• Acute haemolysis 1–3 days after a trigger — pallor, jaundice, dark (cola-coloured) urine, and abdominal/back pain.
• Neonatal jaundice (an important cause in some populations).
• Usually well between episodes.

Investigations & Management

• Blood film during haemolysis — 'bite' cells and Heinz bodies; features of haemolysis.
• G6PD enzyme assay (measure a few weeks after the acute episode, as young reticulocytes have higher enzyme levels and can give a false-normal result).
• Avoid the triggers; supportive care and hydration; blood transfusion for severe haemolysis.

Pathophysiology

• G6PD generates NADPH, which protects red cells against oxidative damage.
• When enzyme activity is low, oxidative stress denatures haemoglobin (forming Heinz bodies), and the spleen removes the damaged cells ('bite cells'), causing acute haemolysis.

Classes of Severity

• The WHO classifies G6PD variants by residual enzyme activity — from severe chronic haemolysis to mild, episodic disease.
• Most affected children have the milder, episodic form triggered by oxidative stress.

Management Summary

• The mainstay is avoidance of oxidative triggers (educate the family, provide a drug list).
• Supportive care during a haemolytic episode; transfusion only if anaemia is severe; treat neonatal jaundice (phototherapy/exchange).

Avoid oxidant drugs, fava beans and naphthalene.