CHEK2 and Haim-Munk syndrome: Lacking definitive studies describing the clinical and biological features of deleterious germline CHEK2 variants in patients with hematopoietic malignancies (HMs), we examined the features of patients and populations with deleterious germline CHEK2 variants and studied a knock-in mouse model of the most common such allele seen in HM patients, CHEK2 p.I157T.