Table 2.

Assignment of likely G6PD Phenotype based on Genotype/Diplotype (CPIC 2014)

Likely phenotypeDefinitionGenotypeWHO class for G6PD variantsaExample of diplotypeb
NormalVery mild or no enzyme deficiency (less than 60% of normal enzyme levels)A male who has a nondeficient (class IV) alleleIVB, Sao Boria
A female who has 2 nondeficient (class IV) allelesIV/IVB/B, B/Sao Boria
DeficientLess than 10–60% of normal enzyme activityA male who has a deficient (class II–III) alleleII, IIIA–, Orissa, Kalyan-Kerala, Mediterranean, Canton, Chatham
A female who has 2 deficient (class II–III variants) allelesII/II, II/III, III/IIIA–/A–, A–/Orissa, Orissa/Kalyan-Kerala, Mediterranean/Mediterranean, Chatham/ Mediterranean, Canton/Viangchan
Deficient with CNSHASevere enzyme deficiency (<10% activity) and associated with CNHSAA male who has a class I alleleIBangkok, Villeurbanne
A female who has 2 deficient (class I variants) allelesI/IBangkok/Bangkok, Bangkok/Villeurbanne
VariablecNormal or deficient enzyme activitycA female who has one nondeficient (class IV) and one deficient (class I–III variants) alleleIV/I, IV/II, IV/IIIB/A–, B/Mediterranean, B/Bangkok

CNSHA, chronic nonspherocytic hemolytic anemia

WHO, World Health Organization

a

WHO classifications (from ref. 14, other details from ref. 17, from (33)). Class I variants are extremely rare; the distinction between class II and III variants is not clear, and the “class V” very high activity variant has been reported in only a single case. Therefore, almost all individuals will have class II, III, or IV alleles. It should be noted that the class of a variant may have been assigned only by the clinical manifestations of an individual in which the variant was subsequently identified.

b

Due to the large number of G6PD variants, many other diplotypes may be possible besides those given as examples here; see Supplementary Table S1 online for a more comprehensive list of variant alleles with their assigned WHO class (33). For HGVS terms, please see the Nomenclature table below.

c

Due to X-linked mosaicism, females heterozygous for one nondeficient (class IV) and one deficient (class I–III variants) allele may display a normal or a deficient phenotype. It is therefore difficult to predict the phenotype of these individuals (Supplementary Material online (G6PD heterozygotes)) (33).

This CPIC table is adapted from (33).

From: Tafenoquine Therapy and G6PD Genotype

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