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Short telomere syndromes constitute a heterogeneous group of clinical conditions characterized by short telomeres and impaired telomerase activity due to pathogenic variants in the essential telomerase components. Dyskeratosis congenita (DC) is a rare, multisystemic telomere biology disorder characterized by abnormal skin pigmentation, oral leukoplakia and nail dysplasia along with various somatic findings.Hoyeraal-Hreidarsson syndrome (HHS) is generally an autosomal recessively inherited subgroup showing growth retardation, microcephaly, cerebellar hypoplasia and severe immunodeficiency. We here report on a consanguineous family from Turkey, in which a missense variant in the reverse transcriptase domain of the TERT gene segregated with short telomere lengths and was associated with full-blown short telomere syndrome phenotype in the index; and heterogeneous adult-onset manifestations in heterozygous individuals.

DNA Topoisomerase IIβ (TOP2B) acts on DNA topology during transcription and has a critical role in neural development. Heterozygous pathogenic changes in its encoding gene, TOP2B (MIM *126431), has been linked with three overlapping phenotypes characterized by immunodeficiency, acral and urogenital anomalies: Hoffman, BILU and Ablepharon‐macrostomia‐like syndrome. We herein report on a mother and two sons with distinct TOP2B‐phenotype. Two males reported further delineated genital phenotype of males and all reported patients were reviewed for genotype–phenotype correlation. We believe the patients reported herein along with the previously defined 11 represent a phenotypic spectrum from mild‐to‐severe immunological, acral and urogenital involvement, for which we propose the acronym “TOP2B‐related Immunodeficiency and Congenital Anomalies Spectrum (TICAS)”.

Human C2orf69 is an evolutionary-conserved gene whose function is unknown. Here, we report 9 children from 5 unrelated families with a fatal syndrome consisting of severe auto-inflammation, progredient leukoencephalopathy with recurrent seizures that segregate homozygous loss-of-function C2orf69 variants. C2ORF69 orthologues, which can be found in most eukaryotic genomes including that of unicellular phytoplanktons, bear homology to esterase enzymes. We find that human C2ORF69 is loosely bound to the mitochondrion and its depletion affects mitochondrial membrane potential in human fibroblasts and neurons. Moreover, we show that CRISPR/Cas9-inactivation of zebrafish C2orf69 results in lethality by 8 months of age due to spontaneous epileptic seizures which is accompanied by persistent brain inflammation. Collectively, our results delineate a novel auto-inflammatory Mendelian disorder of C2orf69 deficiency that disrupts the development/homeostasis of the immune and central nervous systems as demonstrated in patients and in a zebrafish model of the disease.