Immune dysregulation in children with inherited bone marrow failure syndromes and refractory cytopenia of childhood

Inherited bone marrow failure syndromes (IBMFS) are usually identified when patients develop hematologic complications, such as severe BMF, myelodysplastic syndrome or leukemia. In clinical practice, differential diagnosis with refractory cytopenia of childhood (RCC) or autoimmune cytopenia with or without an underlying Inborn Error of Immunity (IEI) may be challenging. To fill this gap, we aim at profiling the immunological landscape associated with pediatric chronic cytopenia(s). We enrolled patients presenting with chronic cytopenia (>12 months): isolated autoimmune cytopenia(s) (AIC, N = 11); IBMFS (N = 12: 4 Diamond-Blackfan; 4 Shwackman-Diamond, 2 Fanconi anemia, 1 RTEL1-Dyskeratosis congenita, 1 RUNX1-deficiency) and RCC (N = 6). Extended immunophenotyping from peripheral blood was performed to compare the AIC to IBMFS and RCC group.Table 1. (abstract: 86) Clinical features of IBMFS and RCC patient cohorts. A, anemia; L, leukopenia; N, neutropenia; T, thrombocytopenia; PAN, pancytopenia; (*) siblings.Empty CellDIAGNOSISMUTATED GENECYTOPENIA LINEAGEADDITIONAL CLINICAL FEATURESAGE AT FLOW ANALYSIS (y)IBMFSDiamond-Blackfan anemia (N=4)RPS19APancreas annularis11ongoingA + L/0,5N.A.AGH deficiency, suppurative sialadenitis, interatrial defect16N.A.AAtrial septal defect21Shwachman Diamond syndrome (N=4)SBDSA + NGH deficiency, pancreatic insufficiency, bone abnormalities, nephrocalcinosis12SBDSNGrowth retardation, pancreatic insufficiency, hepatitis (unknown cause), bone abnormalities, osteopenia15SBDSNGrowth retardation, intestinal malrotation, cleft palate16N.A.NGrowth retardation, pancreatic insufficiency, bone abnormalities18Fanconi anemia (N=2*)BRIP1 (FANCJ)A + T/16BRIP1 (FANCJ)/Precocious puberty, congenital melanocytic nevus9RUNX1 deficiencyRUNX1N + T/15Dyskeratosis congenitaRTEL1PANUpper esophageal stricture19RCCHebo deficiencyERCC6L2N + T/13Refractory cytopenia (N=5)/A + T/16/N + T/14N.A.PAN/9NonePANSeronegative autoimmune hepatitis, eczema, hydronephrosis4NonePANSeronegative autoimmune hepatitis11 Table 1. (abstract: 86) Clinical features of IBMFS and RCC patient cohorts. A, anemia; L, leukopenia; N, neutropenia; T, thrombocytopenia; PAN, pancytopenia; (*) siblings. Lymphocyte subpopulations analysis revealed lower frequencies of CD4 Recent Thymic Emigrants (RTEs) in the IBMFS group (p = 0.020), CD4 naïve T cells in both IBMFS (p = 0.002) and RCC (p = 0.041) patients and CD8 naïve T cells in IBMFS group (p = 0.021), counterbalanced by a higher frequency of CD4 central memory (CM; p = 0.001 for IBMFS; p = 0.022 for RCC) and CD8 CM T cells (p < 0.05 for IBMFS and RCC). A similar profile was detected in both cohorts for naïve Tregs (p < 0.05) towards memory Tregs (p <0.05). We observed a striking T cell immunedysregulation due to an imbalance towards the memory compartment in pediatric patients with RCC and IBMFS. As this scenario is reminiscent of what observed in patients with AIC associated with signs of IEI, further investigations are required to define the pathogenicity of the altered immune homeostasis. Nevertheless, peripheral immunophenotyping confirms to be a useful screening tool able to facilitate differential diagnosis in pediatric cytopenia.Download : Download high-res image (229KB)Download : Download full-size imageFigure 1. Peripheral blood immunophenotyping. Immunological profiling of T cell subpopulations. Lymphocyte frequencies of helper CD4+ T cells, cytotoxic CD8+ T cells and Treg subpopulations. Box plots show the 25th percentile (bottom edge), 50th percentile (median) and 75th percentile (top edge); vertical lines at the top and bottom indicate minimum and maximum values. Grey bars indicate control range, based on age-matched median values. p-values <0.05 (*) or <0.01 (**) are indicated. CM, central memory T cells; EM, effector memory T cells; EMRA, terminally differentiated effector memory T cells. Figure 1. Peripheral blood immunophenotyping. Immunological profiling of T cell subpopulations. Lymphocyte frequencies of helper CD4+ T cells, cytotoxic CD8+ T cells and Treg subpopulations. Box plots show the 25th percentile (bottom edge), 50th percentile (median) and 75th percentile (top edge); vertical lines at the top and bottom indicate minimum and maximum values. Grey bars indicate control range, based on age-matched median values. p-values <0.05 (*) or <0.01 (**) are indicated. CM, central memory T cells; EM, effector memory T cells; EMRA, terminally differentiated effector memory T cells.