The GCase variant E326K has recently been reported to be the most common GBA1 mutation in a British cohort of early‐onset PD cases (≤50 y of age).19 Although this mutation on its own decreases GCase activity, residual activity is still much greater than other GD mutations such as N370S and L444P.20, 21, 22, 23 Although still unproven, heterozygote E326K mutations causing GlcCer accumulation seems unlikely. Here, GBA1 is linked to Parkinson disease.