Classification of G6PD Deficiency Variants by WHO

Class I Enzyme Activity

Severely deficient (<1% activity or not detectable)

Class I Clinical Manifestations

• Chronic

• hereditary nonspherocytic hemolytic anemia (HNSHA)

• severity is variable

• rare

• G6PD-Serres

• G6PD-Madrid

Class I Examples

Class II Enzyme Activity

Severely deficient (<10% activity)

Class II Clinical Manifestations

• Severe, episodic acute hemolytic anemia associated with

  • infections

  • certain drugs

  • fava beans

• not self-limited and may require transfusions during hemolytic episodes

• G6PD-Mediterranean

• G6PD-Chatham

Class II Examples

Class III Enzyme Activity

Mild to moderately deficient (10% to 60% activity)

Class III Clinical Manifestations

• Episodic, acute hemolytic anemia associated with infections and certain drugs

• self-limited

• G6PD-A

• G6PD-Canton

Class III Examples

Class IV Enzyme Activity

Mildly deficient to normal (60% to 150% activity)

Class IV & Class V

No Clinical Manifestations

• G6PD-B (wildtype)

• G6PD-A+ (may also manifest as Class III)

Class IV Examples

Class V Enzyme Activity

Increased (>150% activity)

• naphthalene (mothballs) ⭐️

• fava beans

• red wine

• legumes (garbanzos, kadyos, munggo)

• blueberry

• soya food

• ampalaya

• menthol

(highlighted) some examples of drugs, chemicals, food → vause hemolysis in G6PD deficiency patients