Howard, Matthew T.

Introduction: Chronic myelomonocytic leukemia (CMML), an aggressive myeloid malignancy, can be categorized into two subtypes, proliferative CMML (pCMML) and dysplastic (dCMML), based on a white blood cell (WBC) count of ≥ 13 x 109/L for the former (Arber et al. Blood 2016). While this WBC cut off is somewhat arbitrary, patients with pCMML have unique phenotypic features and a shorter survival. We carried out this study to assess the genomic, transcriptomic and epigenetic landscapes of these two CMML subtypes. Methods: Peripheral blood (PB) and bone marrow (BM) mononuclear cells (MNC) were obtained from WHO-defined CMML patients. Next generation sequencing (NGS) using a 36-gene panel was performed on 350 patients with Illumina HiSeq4000 platform with median read depth of 400X. RNA sequencing (RNA-seq) was performed on 25 patients by bulk whole transcriptome sequencing using Illumina TruSeq. DNA immunoprecipitation sequencing (DIP-seq) was performed on 18 patients using 5-methylcystocine (5mC), 5-hydroxymethylcytosine (5hmC) and bridging monoclonal antibodies with subsequent paired-end sequencing using HiSeq4000. Chromatin immunoprecipitation sequencing (ChIP-seq) was performed on 30 patients with Illumina HiSeq2500 to a depth of 25 million for histone 3 lysine 4 monomethylation (H3K4me1) and histone 3 lysine 4 trimethylation (H3K4me3) and 50 million reads for histone 3 lysine 27 trimethylation (H3K27me3) and Input per sample. Results: Five hundred and seventy-three patients with WHO defined CMML were included; median age 71 years (range 18-95 years), 67% males. 282 patients had pCMML (49%), while 291 (51%) had dCMML. As pre-defined, patients with pCMML were more likely to have higher absolute monocyte counts (p<0.0001), circulating immature myeloid cells (p<0.0001), PB blasts (p<0.0001), and higher lactate dehydrogenase levels (p=0.03). At last follow up 234 (41%) deaths and 70 (20%) leukemic transformations were documented. The median OS for pCMML vs dCMML in this cohort was 19 months vs 30 months (p<0.0001, Figure 1A) and validated in an independent Austrian cohort (p=0.02). Genomic profiling: NGS performed on 350 patients (BM MNC) revealed a higher frequency of NRAS (35 vs 17%, p=0.004), cumulative RAS pathway (NRAS, KRAS, CBL and PTPN11) (73 vs 47%, p=0.001), ASXL1 (p=0.003) and JAK2V617F (p=0.04) mutations in pCMML relative to dCMML (Figure 1B); while dCMML had a higher frequency of SF3B1 mutations (p=0.02). There were no differences in distribution of TET2 and SRSF2Transcriptomic analysis: RNA-seq was performed on PB MNC from RAS pathway mutant pCMML patients (n=12) and RAS pathway wildtype dCMML patients (n=13). Unsupervised clustering analysis resulted in appropriate segregation revealing distinct expression profiles between disease subtypes (Figure 1C). Compared to dCMML, 3729 genes were significantly differentially upregulated and 2658 genes were differentially downregulated in pCMML. Among genes most highly upregulated were mitotic checkpoint kinases including AURBK, PLK1, PLK2, PLK4 andEpigenetic profiling: ChIP-seq of PB and BM MNC from pCMML (n=18) and dCMML (n=12) patients and healthy, age-matched controls (n=10) revealed a global increase in H3K4me1, without significant differences in H3K4me3 or H3K27me3 occupancies (regardless of stratification by ASXL1 mutational status; 40% ASXL1mt in pCMML, 30% dCMML) in pCMML vs dCMML (Figure 1D). H3K4me1 occupancy was also increased in a sequence-specific manner at the transcription start sites of the aforementioned mitotic kinases (PLK1 and WEE1). DIP-seq was performed on PB MNC to assess global differences in 5-mC and 5-hmC levels, between pCMML (n=9) and dCMML (n=9), with no differences seen between the two subtypes (regardless of TET2 mutational status, 40% TET2mt in each subtype) (Figure 1E). Conclusions: Despite the somewhat arbitrary WBC distinction between pCMML and dCMML, clear phenotypic, genetic, transcriptomic, epigenetic and survival differences exist between the two subtypes, providing strong biological rationale for this distinction. pCMML patients have a higher frequency of oncogenic RAS pathway mutations, a unique transcriptomic profile enriched in mitotic check point kinases and a unique chromatin configuration with global and sequence specific enrichment in H3K4me1, with no significant global differences in 5mC, 5hmC, or H3K4me3 and H3K27me3 occupancy. Figure 1 Disclosures Geissler: AOP: Honoraria; Pfizer: Honoraria; AstraZeneca: Honoraria; Novartis: Honoraria; Celgene: Honoraria; Roche: Honoraria; Abbvie: Honoraria; Ratiopharm: Honoraria; Amgen: Honoraria. Al-Kali:Astex Pharmaceuticals, Inc.: Research Funding. Patnaik:Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees.

Abstract Introduction: Chronic myelomonocytic leukemia (CMML) is a chronic myeloid malignancy associated with monocytosis, autoimmunity (~30%) & an inherent risk for leukemic transformation. Bone marrow (BM) dendritic cell (DC) populations occur in ~30% of patients, with a poorly defined biological & prognostic role. The malignant immune microenvironment is regulated by indoleamine 2,3-dioxygenase-1 (IDO-1) expressing DCs, which modulate regulatory T (Treg) cells & block their conversion into proinflammatory T helper (Th17)-like cells. IDO-1 is a known immune checkpoint & functions by catabolizing tryptophan, an amino acid essential for T cell function. We hypothesized that distinct IDO-1 expressing DC populations in CMML modulate Tregs & contribute towards immune tolerance & aggressive disease biology. Methods: Primary diagnostic CMML peripheral blood mononuclear cells (PBMC) & BM biopsy specimens were obtained after Mayo Clinic IRB approval. A DC population was defined on H&E stained biopsy sections as focal collections (>10) of cells with characteristic elongated nuclei & cytoplasmic extensions. Transcriptomic & protein expression studies assessing IDO-1 expression were done by previously described methods. In addition, IHC expression of PD-1, PD-L1 & CTLA-4 was also done. IDO-1 promoter methylation studies with DIP-seq were performed. The impact on immune tolerance was assessed using mass cytometry (CyTOF). Results: Cohort: Twenty eight patients with CMML were included in the study, median age 70 (range: 51-80) years; 71% males. Eleven (39%) patients had coexisting autoimmune conditions. Of these, 8 (73%) had detectable DC populations either at diagnosis, or during the course of their disease. At a median follow-up of 46 (95% CI 27, 84) months, there were 14 (50%) deaths & 9 (32%) leukemic transformations.IHC results: Nine (32%) patients were identified to have a DC population at CMML diagnosis. CD123 & TCL1 staining was performed in 5 (56%) patients, with 3 being positive for both, & 2 positive for CD123 only (additional IHC studies ongoing). IDO1 expression by IHC was documented in all 9 (100%) cases (Fig 1A & 1B), while rare populations of PD-1, PD-L1 & CTLA-4 lymphocytes were also seen in all cases. Due to the low DC burdens (median cellularity ≤ 5%) & uniform staining intensity, IHC-based grading was not done. Samples at serial time-points, post-HMA therapy & at the time of blast transformation, were available in 5 & 3 patients respectively. Among the patients who did not have DC populations at diagnosis, 5 (42%) developed them post-HMA therapy, while 3 (50%) developed them at the time of LT. The development of DC populations was associated with loss of response to HMA (50%) & disease progression (50%).Transcriptomic analysis: RNA expression data was available on 7 (25%) patients, of whom only 1 (14%) had DC populations at diagnosis. The IDO-1 RPKM value in the former was higher than the mean pooled value in the latter group (330 versus 74, p=0.05).Methylation studies: DIP-seq was performed on 12 (43%) cases from the primary IHC cohort. Qualitative analysis of IDO-1 promoter hypomethylation was conducted & confirmed in all 9 (100%) cases with 5-mC & 5-hmC marks compared to input as displayed in figure 1C.Immune profiling: CyTOF was performed on 4 CMML samples (3 with IDO-1 expressing DC populations at diagnosis) from the primary IHC cohort & compared to a normal PBMC control. Results confirmed an increase in DC populations (fig 1D& 1E), & reduced % of Th17-like T cells in CMML samples compared to control (1.1 versus 5.07, p=0.05, fig 1F).Clinical correlates & survival analysis: With the exception that CMML patients with DC populations had a higher frequency of NRAS (P=0.007) mutations, the two groups were comparable for cytogenetic & molecular abnormalities. The median OS for the cohort was 45 (95% CI 29, 84) months. CMML patients with IDO-1 expressing DC populations at diagnosis had a shorter median OS, in comparison to those without (median OS 30 vs 45, p=0.03, Kaplan-Meier analysis in fig 1G). Conclusions: In conclusion, we demonstrate that DC populations are seen in ~30% of patients with CMML with a uniform expression of IDO-1 & limited expression of PD-1, PD-L1 & CTLA-4. CMML patients with BM DC populations have a higher frequency of NRAS mutations & DC IDO-1 expression is associated with tumor induced immune tolerance. Additional IHC, genomic & preclinical studies with IDO-1 inhibitors are ongoing. Figure 1. Figure 1. Disclosures Al-Kali: Novartis: Research Funding.

Abstract Background: Myeloid sarcoma is a tumor mass consisting of myeloid blasts occurring at anatomical site other than the bone marrow (Arber et al. Blood 2016;127(20):2391-2405). It is a subgroup of acute myeloid leukemia, which can be localized or disseminated and may involve multiple organs. It can present with or without a positive bone marrow. It may precede or follow bone marrow involvement. It may be identified at diagnosis or relapse, and is not uncommon after stem cell transplantation (Koc et al. Cancer 1999;85(3):608-615; Yoshihara et al. Biol. Blood Marrow Transplant 2012;18(12):1800-1807). Objective: To describe the clinical characteristics, cytogenetics, prognosis and outcome of patients with myeloid sarcoma with or without bone marrow involvement. Methods: The Mayo Clinic database was interrogated using the ICD-9 codes 205.0, 205.2, 205.3, as well as terms "myeloid sarcoma," "chloroma," and "extramedullary sarcoma" in clinical notes and pathology reports. Patients' follow up information was collected until July 2016. Results: Ninety six patients with a diagnosis myeloid sarcoma were identified. The diagnosis was based on biopsy results and in some cases imaging studies in addition to bone marrow biopsy. The median age was 53 (range 17-83) years, and 64 (67%) patients were males. Myeloid sarcoma with de novo (primary) and secondary acute myeloid leukemia (with antecedent hematologic malignancy and therapy related) accounted for 64% (61) and 36% of the cases respectively. The sites involved based on their frequency of occurrence included integumentary system (skin and soft tissues) in 37 (38%), lymphatic system in 17 (18%), the gastrointestinal and genitourinary system in 14 (15%), the nervous system in 9 (9%), the breast in 3 (3%) and multiple and other single sites in 16 (17 %). Bone marrow cytogenetics findings were documented in 74 (77%) patients; favorable, intermediate, and poor cytogenetic abnormalities account for 7 (9%), 45 (61%), and 22 (30%) cases respectively. After a median follow up of 135 weeks, 57 (59%) patients died. The median survival of primary and secondary acute myeloid leukemia with myeloid sarcoma was 52 and 11.5 months (P<0.0001); and that of favorable, intermediate and unfavorable cytogenetics abnormalities was 169, 52 and 17.5 months (P=0.04) respectively. Twenty six (27%) patients had no bone marrow involvement; and 18 (69%) of them were primary myeloid sarcoma (without antecedent malignancy or therapy). The median (range) age of those with and without bone marrow involvement was 53 (17-83) and 56 (17-81) years (P=0.6). At diagnosis patients with and without bone marrow involvement have a median (range) hemoglobin (gm/dL) (10.3 (6.2-15.4) vs 13.1 (9.9-15.2) P=0.0002), white blood cell count (X109/L) (21.4 (1.1-182.5) vs 5.8 (2.4-23.2) P<0.0001), and platelet count (X109/L) (71 (8-437) vs 250 (17-561) respectively. Aggressive chemotherapy therapy was given to 58 (83%) and 20 (77%) of patients with and without bone marrow involvement (P=0.6). The median survival was 17 and 20 months with and without bone marrow involvement (P=0.4). Of those with bone marrow involvement, 49 (70%) achieved complete remission, and 26 (53%) of those individuals subsequently relapsed. Conclusion: The treatment outcome of patients with myeloid sarcoma with or without bone marrow involvement seems the same. The conventional risk factors, antecedent hematological neoplasms and cytogenetic findings, have significant impact on survival. Disclosures Al-Kali: Celgene: Research Funding; Onconova Therapeutics, Inc.: Research Funding.

Abstract Background : The 2016 revision to the World Health Organization (WHO) classification of myeloid neoplasms has recommended distinction between "proliferative" (WBC ≥ 13 x 10(9)/L) and "dysplastic" (WBC < 13 X 10(9)/L) subtypes of chronic myelomonocytic leukemia (CMML). In the current study of 261 molecularly-annotated cases, we sought to clarify the prognostic relevance of distinguishing proliferative from dysplastic CMML and also describe differences in the distribution of disease-associated mutations. Methods : 261 patients with WHO-defined CMML were included in the study. All patients had bone marrow (BM) biopsies and cytogenetics performed at diagnosis. Targeted capture assays were carried out on BM DNA specimens obtained at diagnosis for the following genes; TET2, DNMT3A, IDH1, IDH2, ASXL1, EZH2, SUZ12, SRSF2, SF3B1, ZRSR2, U2AF1, PTPN11, Tp53, SH2B3, RUNX1, CBL, NRAS, KRAS, JAK2, CSF3R, FLT3, KIT, CALR, MPL, NPM1, CEBPA, IKZF, and SETBP. The 2016 WHO criteria were used to sub-classify CMML into proliferative and dysplastic subtypes. Results :Among the 261 study patients, 65% were males and median age was 70 years. 154 (59%), 64 (25%) and 43 (16%) patients were classified as CMML-0, 1 and 2, respectively. At a median follow-up of 23 months, 174 (67%) deaths and 37 (14%) leukemic transformations were documented. Mutational frequencies were; TET2 45%, ASXL1 45%, SRSF2 40%, NRAS 14%, SETBP1 13%, CBL 10%, JAK2 7%, RUNX1 6%, U2AF1 6%, DNMT3A 6%, SF3B1 5%, ZRSR2 4%, Tp53 4%, IDH2 4%, KRAS 3%, PTPN11 2%, SH2B3 1%, CSF3R 1%, IDH1 1%, EZH2 1%, SUZ12 1%, KIT 1%, FLT3 1%, and CALR 1%. Risk stratification was based on the Mayo Molecular Model: 31% high, 30% intermediate-1, 28% intermediate-2 and 11 % low risk. i) Dysplastic versus proliferative CMML: phenotypic and molecular differences 139 (53%) patients had proliferative and 122 (47%) dysplastic subtypes. There was no difference between the CMML subtypes in terms of age and gender distribution, hemoglobin level, platelet count or BM blast content. Patients with proliferative CMML had higher absolute monocyte counts (AMC) (p<0.0001), circulating immature myeloid cells (IMC, p<0.001), circulating blasts (p<0.001) and serum LDH levels (p=0.01). The following gene mutations were more common in proliferative vs dysplastic CMML: ASXL1 (54% vs 37%, p=0.009), JAK2 (11% vs 3%, p=0.01) and CBL (11% vs 8%, p=0.047); SF3B1 mutations were more common in dysplastic CMML (8% vs 1%, p=0.02). There was no difference in the incidence of TET2, DNMT3A and SRSF2 mutations whereas there was a trend towards a higher prevalence of NRAS (p=0.06) and CSF3R (p=0.06) mutations in proliferative CMML. Cytogenetic abnormalities (p=0.03), including higher risk categories by the Spanish (p=0.03) and the Mayo-French (p=0.01) systems were more common in proliferative CMML. ii) Impact on overall and leukemia-free survival: Median survival for the entire cohort (n=261) was 24 months. In univariate analysis, survival was shorter in patients with proliferative (median 20 months) versus dysplastic (median 29 months) CMML (p=0.008; HR1.5, 95% CI 1.1-2.1; Figure 1A). Other variables of significance, in univariate analysis, included hemoglobin (p=0.001), leukocyte count (p=0.001), AMC (p=0.003), PB blast % (p=0.003), IMC (p=0.01), BM blast % (p=0.045), abnormal karyotype (p=0.02), ASXL1 (p=0.01) and DNMT3A (p=0.0003) mutations. In multivariable analysis, the difference in survival between proliferative and dysplastic subtypes remained significant with the addition of hemoglobin level (p=0.01), PB blast % (p=0.02), IMC (p=0.04), BM blast % (p=0.01) or DNMT3A mutations (p=0.01). This was, however, not the case with addition of leukocyte count (p=0.32), AMC (p=0.18) or ASXL1 mutational status (p=0.14); whereas the adverse impact on survival from the latter three parameters remained significant. The prognostic impact of ASXL1 mutations was most apparent in dysplastic CMML (Figure 1B). There was no difference in leukemic transformation rates (p=0.4). Conclusions: In the context of current prognostic models, sub-classification of CMML into proliferative and dysplastic subtypes might not provide additional prognostic value. The apparent difference in survival between the two subtypes of CMML is probably accounted for by the higher prevalence of leukocytosis/monocytosis and of ASXL1 mutations in proliferative CMML. Disclosures No relevant conflicts of interest to declare.

Abstract Background : DNMT3A mutations result in epigenetic dysregulation and impart a negative prognostic impact in acute myeloid leukemia and myelodysplastic syndromes. In chronic myelomonocytic leukemia (CMML), DNMT3A mutations are seen in 2-5% of patients. In a large Groupe Français des Myélodysplasies (GFM) study (n=312), DNMT3A mutations were seen in 2% and were not included in further survival analyses (Itzykson JCO 2013). In a prior Mayo Clinic study (n=175), DNMT3A mutations were seen in 5% (n=9) and on univariate, but not multivariate analysis (Patnaik Blood C J 2016), were associated with shortened over-all survival (OS). We carried out this study on a larger CMML cohort (n=261), with more (n=15) informative cases to assess the impact of DNMT3A mutations. Methods : 261 patients with World Health Organization (WHO)-defined CMML were included in the study. All patients had bone marrow (BM) biopsies and cytogenetics performed at diagnosis. Targeted capture assays were carried out on BM DNA specimens obtained at diagnosis for the following genes; TET2, DNMT3A, IDH1, IDH2, ASXL1, EZH2, SUZ12, SRSF2, SF3B1, ZRSR2, U2AF1, PTPN11, Tp53, SH2B3, RUNX1, CBL, NRAS, KRAS, JAK2, CSF3R, FLT3, KIT, CALR, MPL, NPM1, CEBPA, IKZF, and SETBP1. The 2016 WHO diagnostic criteria were used. Results: Among the 261 study patients, 65% were males and median age was 70 years (range, 28-91). 154 (59%), 64 (25%) and 43 (16%) patients were classified as CMML-0, 1 and 2, respectively. At a median follow-up of 23 months, 174 (67%) deaths and 37 (14%) leukemic transformations (LT) were documented. Mutational frequencies ≥4% were encountered in; TET2 45%, ASXL1 45%, SRSF2 40%, NRAS 14%, SETBP1 13%, CBL 10%, JAK2 7%, RUNX1 6%, DNMT3A 6%, U2AF1 6%, SF3B1 5%, ZRSR2 4%, Tp53 4%, and IDH2 4%. i) DNTM3A mutated CMML: phenotypic and molecular correlates DNMT3A mutations were seen in 15 (6%) patients; 64% male with a median age of 64 years. DNMT3A amino acid substitutions included; R882H 50%, R882C 29%, R910P 7%, R598* 7% and R320* 7%. The median variant allele frequency burden was 45%. Concurrent gene mutations were detected in; TET2 43%, ASXL1 21%, SF3B1 21%, U2AF1 14%, RUNX1 14%, SETBP1 14%, NRAS 14%, SRSF2 7%, JAK2 7% and Tp53 7%. There was no difference between DNMT3A mutated and wild-type patients in terms of age and gender distribution, hemoglobin level, leukocyte, monocyte (AMC), and platelet counts, peripheral blood (PB) or BM blast content. Concurrent gene mutations were equally distributed with the exception for a higher prevalence of SF3B1 (p=0.003) and a lower prevalence of SRSF2 (p=0.004) mutations in DNMT3A mutated CMML. Four (29%) patients underwent leukemic transformation. ii) Impact on OS and leukemia-free survival (LFS): Median survival for the entire cohort (n=261) was 24 months. In univariate analysis, survival was shorter in DNMT3A mutated (median 8 months) versus wild-type (median 27 months) patients (p=0.0007; HR 2.9, 95% CI 1.5-5.7; Figure 1A). Other variables of significance, in univariate analysis, included lower hemoglobin (p=0.002), higher leukocyte count (p=0.0009), higher AMC (p=0.0012), PB blast % (p=0.001), circulating immature myeloid cells (IMC, p=0.01), BM blast % (p=0.045), abnormal karyotype (p=0.02), and ASXL1 (p=0.01) mutations. Survival was also adversely affected by the presence of either (n=133) or both (n=3) ASXL1/DNMT3A mutations (0=0.007, Figure 1B). In multivariable analysis (MVA) excluding ASXL1 and DNMT3A mutations, hemoglobin (p=0.03), IMC (p=0.013) and AMC (p=0.02) retained significance. When ASXL1 mutations were added to the MVA, ASXL1 (p=0.01) mutations, AMC (p=0.012) and IMC (p=0.03) retained significance. Similarly, when only DNMT3A mutations were added to the MVA, DNMT3A (p=0.003) mutations, IMC (p=0.01) and AMC (p=0.02) retained significance. When both DNMT3A and ASXL1 mutations were added to the MVA, only DNMT3A (p<0.0001) and ASXL1 (p=0.004) mutations remained significant. DNMT3A mutations predicted shortened OS, independent of the ASXL1 inclusive GFM model (p<0.0001) and Mayo Molecular Model (p=0.002). DNMT3A mutations (p=0.0018), along with low hemoglobin levels (p=0.003) independently predicted for a shorter LFS. Conclusions: DNMT3A mutations are seen in ~5% of patients with CMML and impart a negative prognostic impact on both OS and LFS. This finding warrants inclusion of DNMT3A mutations in molecularly integrated CMML prognostic models. Disclosures No relevant conflicts of interest to declare.

Abstract Background: Ring sideroblasts (RS) are erythroid precursors with perinuclear mitochondrial iron accumulation seen in clonal disorders, such as myelodysplastic syndromes (MDS), and non-clonal conditions, including copper deficiency, lead poisoning, and congenital sideroblastic anemias (CSAs). CSAs involve a broad clinical and pathological spectrum related to mutations in ALAS2, ABCB7, etc. or mitochondrial aberrations (Pearson Syndrome; Myopathy, Lactic Acidosis and Sideroblastic Anemia (MLASA); etc.). MDS-RS is often associated with SF3B1 mutations, which have not been reported in other SAs. This study sought to further describe the characteristics and outcomes of patients with CSAs. Methods: After due IRB approval, we retrospectively identified all patients with a CSA diagnosis seen at our institution from 1990-2014. All bone marrow (BM) slides were re-reviewed to confirm the presence of RS. Secondary causes of SA were excluded. Genetic testing on the BM specimen was carried out when possible through research collaborations with the Boston Children's Hospital. Data was retrospectively extracted and is reported in Table 1. Data was analyzed based on the presence or absence of mitochondrial inheritance. Results: Seventeen patients with CSA were identified, 3 (17.6%) with mitochondrial inheritance. In the non-mitochondrial inheritance group, the median age at diagnosis was 29 years (range, 1-61 years). Six (42.9%) were males. At a median follow-up of 119 months (range, 1-401 months), 1 (7.1%) death was documented. The median overall survival (OS) has not been reached. Six of 14 (42.9%) underwent genetic testing, and a mutation was identified in 4 (ALAS -2, FECH -1, and a novel mutation, currently being validated). Six of 6 (100%) samples analyzed for SF3B1 mutations were negative. Median laboratory values at diagnosis included hemoglobin 9.5 g/dL, MCV 85.8, WBC 6.4, and platelets 297,000. Three (21.4%) patients had splenomegaly. Nine (64.3%) had iron overload; 3 (33%) were treated with iron chelation therapy, with only 1 documented response (≥ 500 µg/L reduction in serum ferritin). Twelve (85.7%) were treated with pyridoxine. Outcomes of pyridoxine treatment are described in Table 1. Three of 14 (21.4%) received red blood cell transfusions, and 3 (21.4%) received erythropoiesis stimulating agents (ESA). One (7.1%) patient underwent allogeneic stem cell transplant. Three patients had SAs of mitochondrial inheritance; aberrations were identified in 2 (YARS2 and a 4 kilobase mitochondrial deletion). In this group, the median age at diagnosis was 2 years (range, 1-13 years), and all were males. At a median follow-up of 173 months (range, 119-329 months), 2 (66.7%) deaths were documented. Median laboratory values at diagnosis included hemoglobin 9.0 g/dL, MCV 97.0, WBC 5.2, and platelets 175,000. Conclusions: Congenital SAs are rare, and the majority are of non-mitochondrial inheritance. The molecular basis for disease can be ascertained in less than 50% of patients. Unlike MDS with RS, CSAs are not characterized by the SF3B1 mutation, which may be used to establish clonality. With appropriate supportive care measures, survival for non-mitochondrially inherited CSA remains favorable. Table 1. Demographics and Outcomes for 17 Patients with CSA Age at Diagnosis (Years) Gender Molecular Mutation Additional Features Pyridoxine Response Iron Overload Survival (Months) Outcomes Non-Mitochondrial Inheritance 5 M R452H in ALAS2 N Y2 Y 173 Alive3 3 M Mutation being validated Splenomegaly Y2 Y 254 Alive3 6 M Unknown, PTPN11, ALAS 2, ABCB7 negative Splenomegaly N Y 137 Alive, status-post transplant 29 F Unknown1 N N/A N 131 Alive3 41 F Unknown1 N Y2 N 83 Alive4 40 M Promoter mutation in ALAS2 Splenomegaly N N 106 Alive4 31 F Unknown1 N N Y 401 Deceased 54 M Unknown1 N Lost to follow-up Y 1 Alive3 3 M FECH N N/A N 189 Alive3 1 F SCAD -VUS N Lost to follow-up Y 13 Alive3 29 F Unknown1 N N Y 205 Alive3 58 F Unknown1 N N Y 47 Alive, unknown transfusion status 61 F Unknown1 N Y2 Y 58 Alive3 23 F Unknown1 Alpha-thalassemia-2-trait Y2 N 37 Alive3 Mitochondrial Inheritance 13 M YARS2 MLASA N Y 329 Alive4 2 M Unknown, mitochondrial deletions and ABCB7 negative Myopathy, Ataxia N/A N 173 Deceased 1 M 4 kilobase mitochondrial deletion Pearson Syndrome, B cell lymphoma Y2 N 119 Deceased 1No molecular testing performed 2Sustained hemoglobin response of ≥ 1 g/dL over baseline for ≥ 12 weeks 3Transfusion-independent 4Transfusion-dependent Disclosures Steensma: Incyte: Consultancy; Onconova: Consultancy; Amgen: Consultancy; Celgene: Consultancy.

ObjectiveWe describe a 38‐year‐old woman who presented with a history of inflammatory arthritis, rash, and daily fevers. She was noted to have chronic parvovirus infection with persistently detectable viral titers and a novel mutation in the ELANE gene. ELANE encodes neutrophil elastase, a neutrophil serine protease with important antimicrobial effects, and is found as part of neutrophil extracellular trap (NET) complexes. Pathogenic ELANE mutations have been identified in forms of hereditary neutropenia. However, our patient never had neutropenia. Because of the striking clinical scenario, we investigated this mutation functionally.MethodsNET formation by neutrophils was assessed by scanning electron microscopy. Neutrophil activation and neutrophil elastase production were evaluated by flow cytometry and fluorescent substrate–based functional assay, respectively. A multiplex assay was used to quantitate neutrophil inflammatory cytokine production. PyMOL software was used to generate 3‐dimensional models of mutant elastase.ResultsActivated neutrophils from the patient demonstrated a significantly decreased ability to form NETs on scanning electron microscopy, as well as quantitative defects in neutrophil activation and neutrophil elastase activity. The patient's neutrophils showed altered levels of interleukin‐12 (IL‐12) and IL‐8, which are key cytokines for antiviral immunity and neutrophil chemotaxis. Three‐dimensional mapping revealed that the mutation could alter protein folding and surface charge distribution, potentially perturbing protein trafficking. Thus, the mutation could affect neutrophil function by decreasing NETosis and altering key antiviral activities of neutrophils.ConclusionThis is the first report of a human pathogenic ELANE mutation associated with a defect in NETosis and a distinct syndrome of recurrent viral infection and chronic inflammation.