Genetic variants in NHEJ1 and related DNA repair disorders: insights into phenotypic heterogeneity and links to hypoplastic myelodysplastic syndromes and familial hematological malignancies susceptibility.

This study investigates the burden, phenotypes, progression, and outcomes of familial hematological malignancies (FHM) through clinical evaluation, gene panel testing, and whole exome sequencing, highlighting the significance of identifying genetic causes for personalized treatment. Over six years, 357 patients initially diagnosed with bone marrow failure (BMF) were evaluated, with 152 patients lacking identifiable causes undergoing further analysis. Among these, 53 (34.9%) exhibited features of inherited BMF syndromes, and 13 (24.5%) developed FHM. In a separate cohort of 27 patients with inherited immunodeficiency disorders, 8 (29.6%) developed FHM associated with NHEJ1 or LYST variants, underscoring the familial clustering of hematologic disorders. Notably, 6 of 7 patients from the same family (family-1) with homozygous NHEJ1 variants progressed to secondary myelodysplastic syndrome (sMDS), acute myeloid leukemia (AML), or lymphoma. Among 780 patients diagnosed with hematological malignancies during the study period, 45 (5.8%) were confirmed to have FHM, with 33 patients enrolled for detailed analysis. Of these, 16 (48.5%) had DNA-repair deficiencies (DNA-RD), including eight with Fanconi anemia, six with NHEJ1 variants, and two with BRCA2 mutations. The remaining 17 patients presented conditions such as familial myeloproliferative neoplasms, dyskeratosis congenita (DC) [TERT, DKC1 variants], and Chediak-Higashi syndrome. Two siblings (family-3) with a rare TERT variant and a unique DC phenotype developed sMDS after prolonged BMF. Patients with DNA-RD were younger and exhibited higher rates of growth failure, recurrent infections, and endocrinopathies. These cases frequently progressed to sMDS or AML. A comparative analysis of 319 individuals with DNA double-strand break repair deficiencies revealed a 45% frequency of hematological malignancies. Lymphoma was most common in Nijmegen breakage syndrome (79.4%) while MDS/AML was prevalent in Cernunnos deficiency (66.6%). The findings emphasize the importance of early diagnosis, genetic testing, and personalized management, including timely transplantation, to improve outcomes in FHM. This research underscores the need for clinical awareness and surveillance to facilitate timely interventions and mitigate disease progression.