In recent years, the knowledge about the immune-mediated impairment of bone marrow precursors in immune-dysregulation and autoimmune disorders has increased. In addition, immune-dysregulation, secondary to marrow failure, has been reported as being, in some cases, the most evident and early sign of the disease and making the diagnosis of both groups of disorders challenging. Dyskeratosis congenita is a disorder characterized by premature telomere erosion, typically showing marrow failure, nail dystrophy and leukoplakia, although incomplete genetic penetrance and phenotypes with immune-dysregulation features have been described. We report on a previously healthy 17-year-old girl, with a cousin successfully treated for acute lymphoblastic leukemia, who presented with leukopenia and neutropenia. The diagnostic work-up showed positive anti-neutrophil antibodies, leading to the diagnosis of autoimmune neutropenia, a slightly low NK count and high TCR-αβ+-double-negative T-cells. A next-generation sequencing (NGS) analysis showed the 734C>A variant on exon 6 of the TINF2 gene, leading to the p.Ser245Tyr. The telomere length was short on the lymphocytes and granulocytes, suggesting the diagnosis of an atypical telomeropathy showing with immune-dysregulation. This case underlines the importance of an accurate diagnostic work-up of patients with immune-dysregulation, who should undergo NGS or whole exome sequencing to identify specific disorders that deserve targeted follow-up and treatment.

ANKRD26-related thrombocytopenia (ANKRD26-RT) is characterized by lifelong mild to moderate thrombocytopenia. Patients suffer from an increased susceptibility to acute or chronic myeloid leukemia, myelodysplastic syndrome, or chronic lymphocytic leukemia. We described here a patient with inherited thrombocytopenia initially misdiagnosed as immune thrombocytopenic purpura. A chromosomal deletion involving the ANKRD26 gene was identified. Gene and protein expression analyses suggest an alternative pathogenic mechanism of altered megakaryopoiesis: the synthesis of a chimeric protein with aberrant expression due to the unregulated action of a promoter from a gene located upstream of ANKRD26. This study highlights the importance of advanced genetic testing and functional analysis of patients’ primary cells in the case of the detection of previously unrecognized structural variants in order to understand pathogenic mechanisms. These investigations provided a definitive diagnosis for the patient and facilitated the development of a tailored clinical management strategy, especially concerning the potential for myeloid transformation.

Serine/arginine-rich splicing factors (SRSF) are a family of proteins involved in RNA metabolism, including pre-mRNA constitutive and alternative splicing. The role of SRSF proteins on mitochondria activity has already been shown for SRSF6 but SRSF4 altered expression has never been reported as disease causing. An 8-year-old patient admitted to the Hematology Unit because of leukopenia, lymphopenia, and neutropenia showed a missense variant of unknown significance on the SRSF4 gene (p.R235W) found by Whole Genome Sequencing analysis and inherited by the mother who suffered from mild leuko-neutropenia. Both patients showed lower SRSF4 protein expression compared to HD and altered mitochondrial function and energetic metabolism, which appeared associated with low mTOR phosphorylation and an imbalance in proteins regulating biogenesis (i.e., CLUH) and mitochondrial dynamics (i.e., DRP1, OPA1). Transfection with the wt-SRSF4 gene restored the mitochondrial function. In conclusion, this study shows that the de-scribed variant of the SRSF4 gene is pathogenetic and causes reduced SRSF4 protein expression, which leads to cells’ mitochondrial function impairment. Since mitochondrial function is crucial for hematopoietic stem cells maintenance and some genetic bone marrow failure syndromes display mitochondrial defects, SRSF4 mutation could have substantially contribute to the clinical phenotype of our patient.

Serine/arginine-rich splicing factors (SRSFs) are a family of proteins involved in RNA metabolism, including pre-mRNA constitutive and alternative splicing. The role of SRSF proteins in regulating mitochondrial activity has already been shown for SRSF6, but SRSF4 altered expression has never been reported as a cause of bone marrow failure. An 8-year-old patient admitted to the hematology unit because of leukopenia, lymphopenia, and neutropenia showed a missense variant of unknown significance of the SRSF4 gene (p.R235W) found via whole genome sequencing analysis and inherited from the mother who suffered from mild leuko-neutropenia. Both patients showed lower SRSF4 protein expression and altered mitochondrial function and energetic metabolism in primary lymphocytes and Epstein–Barr-virus (EBV)-immortalized lymphoblasts compared to healthy donor (HD) cells, which appeared associated with low mTOR phosphorylation and an imbalance in the proteins regulating mitochondrial biogenesis (i.e., CLUH) and dynamics (i.e., DRP1 and OPA1). Transfection with the wtSRSF4 gene restored mitochondrial function. In conclusion, this study shows that the described variant of the SRSF4 gene is pathogenetic and causes reduced SRSF4 protein expression, which leads to mitochondrial dysfunction. Since mitochondrial function is crucial for hematopoietic stem cell maintenance and some genetic bone marrow failure syndromes display mitochondrial defects, the SRSF4 mutation could have substantially contributed to the clinical phenotype of our patient.