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Table 1 G6PDd variant types

From: Spatial distribution of G6PD deficiency variants across malaria-endemic regions

Type Residual enzyme activity Population-level prevalence Clinical significance Primaquine-associated public health concern
Type 1 <10% Sporadic (never polymorphic) Severe and chronic: CNSHA None – too rare
Type 2§ <1-50% Polymorphic Asymptomatic until exposed to an exogenous trigger Yes – commonly inherited and cause individuals to be at risk of haemolysis
Type 3 Normal (>50%) Polymorphic (wild-type) None None – G6PD normal
  1. §Type 2 variants have previously been separated into Class II and Class III variants of the WHO-endorsed G6PDd variant classification[28, 29]. For many variants, however, this subdivision is blurred and poorly defined[25].