Bone Marrow Failure Syndromes: Clinical and Genetic Characterization in TERT-associated Dyskeratosis Congenita.

BACKGROUND: Bone marrow failure syndromes (BMFs) comprise a heterogeneous group of genetic disorders characterized by impaired hematopoiesis and multisystem involvement. Dyskeratosis congenita (DC) is a telomere biology disorder caused by defects in telomerase or telomere maintenance, leading to progressive BMF and variable extra-hematopoietic manifestations. OBJECTIVES: To describe the clinical, immunologic, genetic, and telomere biology findings in a patient with DC caused by a novel biallelic telomerase reverse transcriptase (TERT) mutation, and to highlight diagnostic and therapeutic considerations in telomere-associated BMFs. METHODS: We assessed cellular and humoral immune functions. Genetic analysis was conducted using whole-exome sequencing (WES) with segregation analysis. Telomere length was assessed by flow-FISH. Functional and radiologic evaluations were performed to define disease extent. RESULTS: A 2-year old male born to consanguineous parents presented with multisystemic clinical features, and hypocellular bone marrow. WES identified a novel homozygous TERT missense variant (c.3052G>A; p.Ala109Thr) supported by markedly shortened telomeres. Neuroimaging revealed cerebellar hypoplasia consistent with Hoyeraal-Hreidarsson syndrome. Immunologic evaluation demonstrated skewed CD4:CD8 ratios. An incidental heterozygous MEN1 variant was also detected. CONCLUSIONS: We expand the clinical and genetic spectrum of TERT-associated DC and illustrate the critical role of genomic diagnostics and telomere assessment in BMFs. Early molecular diagnosis enables targeted evaluation, informs prognosis, and guides personalized management in telomere biology disorders. In addition, the identification of actionable secondary variants further highlights both the power and complexity of comprehensive genomic testing.