Restricting our meta-analysis to studies that searched for second hits suggested that PD risk was larger in the carriers of single PRKN CNVs (OR = 3.11, 95% CI: 1.23, 7.89, P = 0.016; I2 = 0.0%, Phet = 0.879) compared with those harbouring heterozygous SNVs (OR = 1.59, 95% CI: 0.79, 3.20, P = 0.191; I2 = 0.0%, Phet = 0.785). The gene discussed is PRKN; the disease is Parkinson disease.