tags:
  - paeds/haemato

G6PD Deficiency

Definition

G6PD (glucose-6-phosphate dehydrogenase) deficiency is an enzymatic defects involving hexose monophosphate pathway.

the most common enzymatic defects
X-linked recessive (more common in males)
resistant to falciparum malaria

Pathophysiology

G6PD catalyzes the conversion of glucose 6-phosphate to 6-phosphogluconic acid → produces NADPH wich maintain GSH → GSH provide protection against oxidant threats (drugs, infections) → prevent RBC from precipitate (Heinz bodies) or damage RBC membrane

Clinical Syndromes

1. Acute hemolytic anemia

it is episodic

2. Chronic nonspherocytic hemolytic anemia

Clinical Manifestation

neonatal jaundice
acute hemolytic anemia
- acute
- induced by infections, certain drugs, fava beans
- occur after 24-48hrs of ingestion of substance with oxidant properties
- Drugs: aspirin, sulfonamides, rasburicase, and antimalarials (primaquine)
- Fava beans: contain divicine, isouramil, convicine -> lead to production of hydrogen peroxide & reactive oxygen products

Lab Findings

FBC: anemia, low HCT
High haptoglobin
Heinz bodies
RBC inclusions - seen within 3 to 4 days of illness
Bite cells
Polychromasia (bluish, larger RBC)
Reticulocytosis

Diagnosis

Screening test: decoloration of methylene blue, reduction of methemoglobin, or fluorescence of NADPH
Reduced G6PD activity in RBC with high reticulocyte count
Should be considered in any neonatal hyperbilirubinemia & borderline-low G6PD activity

Prevention & Treatment

Prevention of hemolysis constitutes the most important therapeutic measure.
When possible, males belonging to ethnic groups with a significant incidence of G6PD deficiency (e.g., Greeks, southern Italians, Sephardic Jews, Filipinos, southern Chinese, Americans of African descent, Thais) should be tested for the defect before known oxidant drugs are given.
The usual doses of aspirin and trimethoprim-sulfamethoxazole do not cause clinically relevant hemolysis in the A− variety. Aspirin administered in doses used for acute rheumatic fever (60-100 mg/kg/24 hr) may produce a severe hemolytic episode.
Infants with severe neonatal jaundice who belong to these ethnic groups also require testing for G6PD deficiency because of their heightened risk for this defect.
If severe hemolysis has occurred, supportive therapy may require blood transfusions, although recovery is the rule when the oxidant agent is discontinued.

Reference

Nelsons pg 4470/6873