Revised World Health Organization (WHO) classification of G6PD gene variants: Relevance to neonatal hyperbilirubinemia.

The WHO recently revised their classification schema for G6PD gene variants. Notably, the previously separate Class II (severe enzyme deficiency; <10 % normal) and Class III (moderate enzyme deficiency; 10-60 % normal) variant groups are now combined into a single new category designated as Class B. Class B variants exhibit G6PD enzymatic activity in the <45 % of normal range. This welcome and prudent reclassification far better aligns with the neonatal hyperbilirubinemia risk reported in neonates with i) former "less severe" Class III variants including G6PD A- and ii) female neonates heterozygous for deficient alleles.