PAX5 and precursor B-cell acute lymphoblastic leukemia: Comment: The following three factors provide substantial evidence for the hypothesis that hereditary B-ALL is associated with PAX5 deficiency: (1) the presence of a likely pathogenic variant in PAX5 (a B-ALL high-susceptibility gene), (2) a 50% VAF observed in samples from most of the family members, strongly suggesting a germline etiology, and (3) the diagnosis of B-ALL in several family members.