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BACKGROUND Bacillus subtilis (B. subtilis) is considered a non-pathogenic microorganism of the genus Bacillus and a common laboratory contaminant. Only scarce reports of B. subtilis central nervous system infection have been reported, mainly in the form of pyogenic meningitis, usually in cases of direct inoculation by trauma or iatrogenically. CASE SUMMARY A 51-year-old man, with a free previous medical history, presented to the Emergency Department of our hospital complaining of recurrent episodes of left upper limb weakness, during the last month, which had been worsened the last 48 h. During his presentation in Emergency Department he experienced a generalized tonic-clonic grand mal seizure. Brain magnetic resonance imaging (MRI) scan with intravenous Gadolinium revealed a 3.3 cm × 2.7 cm lesion at the right parietal lobe surrounded by mild vasogenic edema, which included the posterior central gyrus. The core of the lesion showed relatively homogenous restricted diffusion. Post Gadolinium T1W1 image, revealed a ring-shaped enhancement. Due to the imaging findings, brain abscess was our primary consideration. Detailed examination for clinical signs of infectious foci revealed only poor oral hygiene with severe tooth decay and periodontal disease, but without detection of dental abscess. The patient underwent surgical treatment with right parietal craniotomy and total excision of the lesion. Pus and capsule tissue grew B. subtilis and according to antibiogram intravenous ceftriaxone 2 g bids was administered for 4 wk. The patient remained asymptomatic and follow-up MRI scan two months after operation showed complete removal of the abscess. CONCLUSION This case highlights the ultimate importance of appropriate oral hygiene and dental care to avoid potentially serious infectious complications and second, B. subtilis should not be considered merely as laboratory contaminant especially when cultivated by appropriate central nervous system specimen.

Introduction: Immunotherapy with Chimeric Antigen Receptor T cells (CAR-Τ) is a promising innovative treatment for refractory B cell malignancies offering a considerable chance for long-term survival in patients (pts) with an otherwise dismal prognosis. Since January 2020, two anti-CD19 CAR T cell products have been introduced into clinical practice in Greece: a) tisagenlecleucel (Kymriah) for adults with relapsed/refractory diffuse large B-cell Lymphoma (r/r DLBCL) including transformed follicular lymphoma (TFL), as well as for children or young adults with relapsed/refractory B cell acute lymphoblastic leukemia (B-ALL), and b) axicabtagene ciloleucel (Yescarta) for adults with r/r DLBCL including TFL and primary mediastinal B-cell lymphoma (PMBCL). The aim of this study was to present the real-world experience of the initial application of CAR T cell therapy in adult pts in Greece, with special focus on early toxicity and disease outcomes. Methods: Data from all consecutive pts were collected from the two transplant centers which were initially accredited for CAR T cell therapies in adult pts: Evangelismos Hospital, Athens and George Papanicolaou Hospital, Thessaloniki. Between November 2019 and July 2021, 51 pts were referred for CAR T cell treatment. In 41 pts lymphocyte collection was performed and product manufacturing was successfully completed in 35; in 2 pts insufficient cell expansion was noted and in 4 manufacturing was terminated due to disease progression and patient death. Results: From January 2020 until July 2021, CAR T cells were infused in 27 pts; 3 pts could not receive the product due to clinical deterioration/death and 5 pts are presently being scheduled for infusion. Of the 27 treated pts, 16 received tisagenlecleucel and 11 axicabtagene ciloleucel. The median age of infused pts was 49 (18-69) years. Diagnosis was DLBCL (n=16), PMBCL (n=3), TFL (n=2), B-ALL (n=6), and the median number of previous lines of treatment was 4 (2-5). Five pts with lymphoma had undergone autologous, and 4 pts with B-ALL allogeneic stem cell transplantation. In total 18/27 pts received bridging therapy, including radiotherapy (n=5), chemoimmunotherapy (n=9), steroids (n=3), and inotuzumab ozogamicin (n=1). The median time from leukapheresis to product delivery and infusion was 35 (15-81) and 59 (35-152) days, respectively. All pts received lymphodepleting therapy before CAR T cell infusion with combination of cyclophosphamide and fludarabine. For patient monitoring, prophylactic therapy and management of toxicity, the EBMT (Yakoub-Agha I, et al. Haematologica 2020) and MD Anderson (Neelapu S, et al. Nat Rev Clin Oncol 2018) guidelines were adopted. Twenty-six pts developed neutropenia (grade II: 2, grade IV: 24) and 20 thrombocytopenia (grade I: 7, grade II: 3, grade III: 1, grade IV: 9), with a median duration of 11 (4-132) and 20 (3-150) days, respectively. Cytokine release syndrome (CRS) and neurotoxicity (ICANS) were noted in 21 (grade I: 8, grade II: 7, grade III: 6) and 5 (grade I: 3, grade III: 2) pts, respectively. Tocilizumab was administered for CRS according to guidelines, and steroids were additionally required for CRS and/or ICANS in 12 pts. In 2 pts, persistent ICANS necessitated further treatment with anakinra (n=2), siltuximab (n=1), and cyclophosphamide (n=1). Hypogammaglobulinemia was encountered in 14/27 pts. With a median follow-up of 7.3 (1-17) months, overall response rate was 48% with 12 (45%) pts being currently in complete remission (CR). No treatment related mortality was observed. Disease-free (DFS) and overall survival (OS) were 52% and 85.3% at 1-year, respectively. DFS and OS were significantly associated with baseline LDH levels (p=0.017 and 0.050, respectively) and grade II/III CRS (p=0.041 and 0.015, respectively, Figure). Conclusions: Despite the limited experience in the real-world setting, CAR T cell therapy can be administered safely and may successfully rescue patients with DLBCL or B-ALL who lack alternative treatment options. Close monitoring of patients and prompt recognition and management of side effects are mandatory for achieving the benefits of therapy. Figure 1 Figure 1. Disclosures Baltadakis: WinMedica: Other: Travel Grants; Gilead: Other: Travel Grants; Genesis Pharma: Other: Travel Grants; Abbvie: Honoraria; Novartis: Honoraria; Gilead: Honoraria; Pfizer: Honoraria, Other: Travel Grants; Astellas: Honoraria; Alexion: Honoraria; Bristol-Myers Squibb: Honoraria; Amgen: Honoraria; Baxalta Hellas: Other: Travel Grants. Gavriilaki: Pfizer Corporation: Research Funding; Gilead Corporation: Honoraria; Alexion, Omeros, Sanofi Corporation: Consultancy. Tzannou: Allovir: Current equity holder in publicly-traded company; Gileas: Honoraria. Anagnostopoulos: Abbvie: Other: clinical trials; Sanofi: Other: clinical trials ; Ocopeptides: Other: clinical trials ; GSK: Other: clinical trials; Incyte: Other: clinical trials ; Takeda: Other: clinical trials ; Amgen: Other: clinical trials ; Janssen: Other: clinical trials; novartis: Other: clinical trials; Celgene: Other: clinical trials; Roche: Other: clinical trials; Astellas: Other: clinical trials .

Feasibility of haploidentical stem cell transplantation (haploSCT) is enhanced by use of post-transplant cyclophosphamide (PTCY). Despite preservation of non-alloreactive T cells, delayed reconstitution of cellular immunity and viral reactivation may compromise the outcome of T cell replete haploSCT. The study included 47 patients, aged 19-70 (median, 53) years, who underwent haploSCT with PTCY for myeloid (n=35) or lymphoid (n=12) malignancies. Myeloablative conditioning was mainly utilized (n=36). Graft source was peripheral blood (n=29) or bone marrow (n=18). Cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus-6 (HHV-6) reactivation was monitored by real-time quantitative PCR (RQ-PCR) in plasma and/or leukocytes weekly for at least 6 months. BK virus (BKV) reactivation was assessed by RQ-PCR in urine and/or blood in cases with hemorrhagic cystitis (HC). Preemptive therapy was the principal modality for CMV infection in all but 1 patient who received letermovir prophylaxis. Reconstitution of cellular immunity was assessed by flow cytometry. With a median follow-up of 30 months, cumulative incidences (CIN) of relapse and non-relapse mortality were 13.4% (95% CI, 5.4-25.1%) and 31.4% (95% CI, 18.3-45.4%) at 2 years, respectively. Disease-free and overall survival were 55.2% (95% CI, 42.3-72.1%) and 61.8% (95% CI, 48.9-78.1%) at 2 years, respectively. CIN of CMV reactivation (>100 copies/ml) plateaued at 75.6% (95% CI, 60.1-85.7%) at 3 months. CMV infection developed in 34/45 patients at risk. Recurrent CMV infection occurred in 17/34 with median 1.5 (range, 1-6) episodes per patient. Median duration of anti-CMV therapy was 27 (range, 14-199) days. CMV disease was documented in 2 patients. CIN of EBV reactivation (>1,000 copies/ml) was 47.1% (95% CI, 34.2-63.9%) at 1 year, and preemptive therapy with rituximab was required in 2 patients. HHV-6 reactivation (>1,000 copies/ml) was observed in 6 patients (CIN, 10.6% at 6 months; 95% CI, 3.8-21.4%). CIN of BKV-related HC reached 27.7% (95% CI, 15.7-40.9%) at 3 months. Cystoscopy was required in 5/13 and nephrostomy in 1/13 patients. Reconstitution of T cell immunity was considerably delayed, with median CD4+ cell counts of 83/uL (range, 7-337), 216/uL (range, 80-509), and 236/uL (range, 97-586) at 3, 6 and 12 months, respectively. Recurrent CMV infection was associated with the recovery of CD4+ cells at 3 months (Figure, median CD4+ count of 191/uL versus 62/uL in patients with 1 or ³2 episodes of CMV reactivation, respectively; p=0.009). Haplo-SCT with PTCY is associated with substantial rates of viral reactivation resulting in the need for prolonged antiviral therapy and considerable morbidity as well. Strategies to prevent viral infection are strongly warranted. The timing and duration of such interventions (like letermovir or adoptive immunotherapy) may be guided by the tempo of immune reconstitution.

Introduction: The preferred method for haploidentical stem cell transplantation (haploSCT) is currently the use of post-transplantation cyclophosphamide (PTCY) since it obviates the need for depletion of T lymphocytes, which is associated with profound immunosuppression. Despite preservation of non-alloreactive donor T cells, reconstitution of pathogen-specific immunity may be delayed even after T cell replete haploSCT. The incidence and clinical sequelae of viral reactivation may thus compromise the outcomes of the procedure. Patients and Methods: The study included 47 patients, who underwent haploSCT with PTCY from 12/2013 until 05/2019 and achieved stable donor engraftment. Median age at transplant was 53 years (range, 19-70). The indications for transplant were acute myeloid (n=19) or lymphoblastic (n=10) leukemia, myelodysplastic syndrome (n=10), myelofibrosis (n=4), chronic myeloid (n=2) or lymphocytic (n=1) leukemia, and T-prolymphocytic leukemia (n=1). Myeloablative conditioning was mainly utilized (n=36), with the exception of certain patients who received reduced-intensity (n=10) or non-myeloablative (n=1) regimens. The graft source was peripheral blood in 29 and bone marrow in 18 cases. Tacrolimus in combination with mycophenolate mofetil was administered for prevention of graft-versus-host disease. Recipient/donor cytomegalovirus (CMV) serostatus was -/- (n=2), -/+ (n= 5), +/- (n=11), or +/+ (n=29). CMV, Epstein-Barr virus (EBV), and human herpesvirus-6 (HHV-6) reactivation was monitored by real-time quantitative PCR (RQ-PCR) in plasma and/or leukocytes weekly for at least 6 months post haploSCT. BK virus (BKV) reactivation was assessed by RQ-PCR in urine and/or blood specimens in cases with symptoms suggestive of hemorrhagic cystitis (HC). Prophylaxis with letermovir was available in 1 patient only, and preemptive antiviral therapy was the principal modality for the management of CMV infection. Cellular immunity reconstitution was assessed by flow cytometry at 3, 6, and 12 months after transplant. Results: With a median follow-up time of 30 months (range, 2-64), the cumulative incidences (CIN) of relapse and non-relapse mortality (NRM) were 13.4% (95% confidence interval [CI], 5.4-25.1%) and 31.4% (95% CI, 18.3-45.4%) at 2 years, respectively. Disease-free (DFS) and overall survival (OS) were 55.2% (95% CI, 42.3-72.1%) and 61.8% (95% CI, 48.9-78.1%) at 2 years, respectively. The CIN of CMV reactivation (>100 copies/ml) plateaued at 75.6% (95% CI, 60.1-85.7%) at 3 months. CMV infection developed in 34 out of 45 patients who were at risk, whereas recurrent CMV reactivation was observed in 17 patients with a median number of 1.5 episodes (range, 1-6) per patient. The median total duration of antiviral therapy for CMV infection was 27 days (range, 14-199). CMV disease (pneumonia) was documented in 2 patients. The CIN of EBV reactivation (>1,000 copies/ml) was 47.1% (95% CI, 34.2-63.9%) at 12 months. No case of EBV-related post-transplant lymphoproliferative disorder was observed, however preemptive therapy with rituximab was required in 2 patients with rapidly increasing EBV viral load. HHV-6 reactivation (>1,000 copies/ml) was observed in 6 patients (CIN, 10.6% at 6 months; 95% CI, 3.8-21.4%), but only one required therapy with foscarnet due to high viral load (>10,000 copies/ml). The CIN of BKV-related HC reached 27.7% (95% CI, 15.7-40.9%) at 3 months. Cystoscopy for bladder hemostasis was required in 5/13 and nephrostomy in 1/11 patients with HC. Reconstitution of helper T cell immunity was considerably delayed, with median absolute CD4+ cell counts of 83/uL (range, 7-337), 216/uL (range, 80-509), and 236/uL (range, 97-586) at 3, 6 and 12 months, respectively. Recurrent CMV infection was significantly associated with the recovery of CD4+ cells at 3 months (Figure; median CD4+ count of 191/uL versus 62/uL in patients with 1 and 2 or more episodes of CMV reactivation, respectively; p=0.009). Conclusions: HaploSCT with PTCY is associated with substantial rates of viral reactivation (especially CMV and BKV) resulting in the need for prolonged antiviral therapy and considerable morbidity. Strategies to prevent viral infection are strongly warranted in haploidentical stem cell transplantation. The timing and duration of such interventions (like letermovir or adoptive immunotherapy) may be guided by the tempo of immune reconstitution following haploSCT. Figure Disclosures Tsonis: Gilead: Other: Travel Grant; Astellas: Other: Travel Grants; Gilead: Other: Travel Grant; Aenorasis: Other: Travel Grant; Takeda: Other: Travel Grant; Pfizer: Other: Travel Grant; Innovis: Other: Travel Grant.

Introduction Lower respiratory tract infections (LRTI) due to parainfluenza (PIF) or respiratory syncytial virus (RSV) represent a major challenge for immunocompromised patients especially those after allogeneic stem cell transplantation (allo-SCT). Evidence-based guidelines for the management of respiratory virus infections in allo-SCT recipients are limited due to the paucity of effective antivirals and the lack of prospective randomized trials. In this study, we report our experience with the use of oral ribavirin with or without the addition of IVIgG in allo-SCT recipients with LTRI due to RSV and PIF. Patients and methods This is a retrospective study performed in 3 BMT centers in Athens, Greece (2 adult and 1 pediatric center). Review of medical records was performed with the aim to identify patients with RTIs who received treatment with oral ribavirin. LRTI was defined according to the European Conference on Infections in Leukaemia (ECIL-4) (Ref 1). Presence of RSV or PIF in specimens from nasopharyngeal wash and/or BAL was documented with the use of a PCR assay. Ribavirin was administered at a dose of 20-30mg/kg divided into 4 daily doses, with appropriate dose adjustment according to creatinine clearance. Treatment with ribavirin was continued until significant symptomatic and radiological improvement. Co-administration of IVIgG was at the discretion of the treating physician and was mostly based on the availability of IVIgG and on the severity of underlying illness. IVIgG was administered at a daily dose of 400mg/kg for a total dose of 2 g/kg. Informed consent was given by patients or their parents. Results Forty-nine episodes of LRTI due to RSV or PIF were reported during a nine-year period in 7 children and 37 adult patients after allo-SCT. Three children and 2 adult patients had a second LRTI due to RSV, 6, 8, 8, 10 and 12 months after the first episode. Patient's characteristics are shown in Table 1. All patients presented with fever and cough. In almost all of the patients auscultation revealed a prolonged expiratory phase, diffuse wheezing, while the presence of crackles was more prominent finding in patients presenting with pneumonia. Arterial blood gas analysis showed moderate to severe hypoxemia. In 32 out of 49 episodes oxygen supplementation was required while 7 patients required mechanical ventilation. All 49 episodes treated with oral ribavirin while in 37 cases ribavirin was administered in combination with IVIgG. High resolution CT-scan was performed in 41 episodes and revealed bilateral abnormalities in all patients examined. Small centrilobular nodules, bronchial wall thickening (32 out of 41 episodes) and ground-glass opacities (21 out of 41 episodes) were common findings, while a pattern of diffuse air-space consolidation was observed in 11 cases. In 43 LRTI episodes a rapid response to treatment in a median of 3 days (range, 2 - 5) was observed. Complete resolution of all symptoms and signs of disease occurred after a median of 9 days (7 - 20) of treatment. One patient with pneumonia due to PIF3 who needed mechanical ventilation had a complete resolution of all symptoms of disease. Six deaths attributable to LRTI were observed among a total of 49 episodes (all 6 patients were in need for mechanical ventilation). Disease relapse confirmed microbiologically occurred in only 1 patient with LRTI due to RSV 10 days after the end of treatment with ribavirin. One children developed bronchiolitis obliterans syndrome (BOS) 9 months after the resolution of RSV infection. Cryptogenic organizing pneumonia (COP) was observed in two patients 1 and 2 months after the complete resolution of LRTI due to PIF. Both patients had an excellent response to treatment with steroids. Conclusions Oral Ribavirin has an excellent efficacy and safety profile. Complete and fast resolution of infection occurred in 88% of cases. From the present study it is not clear if the addition of IVIgG offers any therapeutic benefit. References Fourth European Conference on Infections in Leukaemia (ECIL-4): Guidelines for Diagnosis and Treatment of Human Respiratory Syncytial Virus, Parainfluenza Virus, Metapneumovirus, Rhinovirus, and Coronavirus. Clin Infect Dis 2013;56(2):258-66 Disclosures Tsonis: Gilead: Other: Travel Grant; Astellas: Other: Travel Grants; Innovis: Other: Travel Grant; Pfizer: Other: Travel Grant; Takeda: Other: Travel Grant; Aenorasis: Other: Travel Grant. OffLabel Disclosure: Tabl Ribavirin. Current indication: Treatment of active hepatitis C in combination with interferon-a.

Objectives To report a case of intravascular lymphoma (IVL) in a Caucasian patient who presented with anasarca as his sole clinical sign. Material and Methods A man presented with anasarca-type oedema and fatigue. After excluding heart failure, hepatic cirrhosis, nephrotic syndrome, hypothyroidism, AL-amyloidosis and adverse drug reaction which can all cause oedema, we turned our attention to capillary permeability disorders. Results Closer review of the bone marrow aspirate demonstrated haemophagocytic histiocytosis, while core, renal and duodenal biopsies showed a B-cell IVL. Conclusion The differential diagnosis of anasarca, a relatively common clinical sign, should include IVL although the diagnosis may still be challenging. LEARNING POINTS Anasarca-type oedema is an unusual initial presentation of intravascular lymphoma (IVL) and is normally attributed to capillary permeability disorders. Two clinical forms of IVL have been recognized: a Western form and an Asian variant which is characterized by haemophagocytosis. Patients of Caucasian origin who have the clinical features of the Asian variant of IVL make the diagnosis of this condition even more challenging.

Background and Methods: Systemic Mastocytosis (SM) is a rare haematologic malignancy characterized by the abnormal growth and accumulation of neoplastic mast cells in one or more organs. The cKIT D816V mutation is a common genetic finding in most cases. A subset of patients appears to be at increased risk for mediator release related symptoms as well as organ dysfunction, including skeletal problems such as osteoporosis, osteolytic lesions and fractures. The diversity of clinical manifestations results in both delayed diagnosis and therapeutic dilemmas. SM cases diagnosed in Greece, between 1987 and 2018, are presented. This project is included in the current activities of Myeloproliferative Neoplasm Working Party of Hellenic Society of Haematology for registry and research development. The medical files of the patients were retrospectively evaluated for disease characteristics, treatment and outcome. Results: Overall 59 patients, median age 52.0 years, with SM were included in the study. Median time of symptoms onset to diagnosis was two years. Twenty-one patients were categorized as indolent SM (ISM), 19 as SM with an associated haematological neoplasm (SM-AHN), 18 as aggressive SM (ASM) and one with mast cell leukaemia (MCL). The main characteristics of the disease are shown in Table 1. Several haematologic neoplasms were associated with SM. Although myeloid malignancies were the most common, including MDS or MDS/MPN (n=9), CMML (n=2), AML (n=1), CML (n=1) and ET (n=1), lymphoid malignancies were also reported and included NHL (n=3), HL (n=1) and B-ALL (n=1). SM and the AHN were diagnosed simultaneously in 12 cases. AHN diagnosis preceded the diagnosis of SM in 4 cases (median time: 22 months), while the opposite occurred in three cases (median time: 7.0 months). Most of the patients with ISM (16/21) did not receive any specific treatment. As far as the remaining five are concerned, one was treated with imatinib, one with hydroxyurea and the rest three received corticosteroids to control the mediators' related symptoms. One of the latter had diarrhoea without infiltration of the gastrointestinal tract and received consecutively Interferon alpha (IFNα), imatinib and corticosteroids without resolution of the syndrome. Eight patients with SM-AHN received treatment for both the SM and the co-existing haematological neoplasm, six only for the AHN, three only for SM, while three did not require treatment yet. The most common treatment for SM was IFNα (n=6), followed by imatinib (n=4), cladribine (2-CdA) (n=3) and dasatinib (n=1). Patients with ASM received either IFNα (n=8) or 2-CdA (n=5) as first line treatment. Second line treatment included imatinib (n=2), 2-CdA due to IFNα intolerance (n=1) and corticosteroids (n=2). Two patients with vertebrae fractures required surgical intervention. All patients with skeletal involvement received additionally biphosphonates. The patient with MCL received consecutively 2-CdA, chemotherapy (FLAG-Ida) and dasatinib achieving partial response and proceeded to allogeneic stem cell transplantation. He died 6 months later due to complications related to graft versus host disease. With a median follow-up of 31 months the median overall survival in the entire cohort is not reached. The median follow-up for patients with ISM and ASM is 33.5 and 18.5 months respectively, and all of them are alive with adequate disease control. Seven deaths were reported only in the group of patients with SM-AHN. Six patients died due to acute leukaemia and one due to infection, indicating that the aggressiveness of the underlying haematological malignancy is the strongest factor that affects survival in this group. Conclusion: Systemic Mastocytosis is a rare disease with variable manifestations and outcome. Nowadays, several therapeutic modalities are available for effective disease management over time. Novel targeted therapies seem to be promising to further improve the outcome, but still early and accurate diagnosis, in accordance to WHO classification, remains important. Table 1. Table 1. Disclosures Gavriilaki: European Hematology Association: Research Funding. Terpos:Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant, Patents & Royalties; Genesis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel Grant, Patents & Royalties; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria.

The detection of concurrent JAK2V617F and BCR-ABL mutations is uncommon; an incidence of 2.5% is reported in the literature. Scarce data indicate that the coexistence of JAK2V617F mutation and BCR-ABL translocation may denote an adverse prognostic factor for CML. Recently, the occurrence of novel Calreticulin (CALR) mutations in JAK2/MPL unmutated ET or PMF was reported. To our knowledge, no CALR mutations have been described so far in the context of BCR-ABL positive MPNs. We present 3 cases with molecularly defined diagnosis of another type of MPN in addition to Ph+ CML, including one patient with the novel finding of a CALR mutation in conjunction with the BCR-ABLtranslocation, and we infer a possible mechanism for the emergence of a second MPN clone upon treatment of the initial MPN. A 32 yr old female was diagnosed in 1999 with ET on the basis of marked thrombocytosis in the absence of any underlying cause. She was treated with INF-α and subsequently with anagrelide. Six years later (2005) and while the CBC was normal, cytogenetic and molecular studies disclosed the presence of Ph1 chromosome in 4/20 metaphases and BCR-ABL transcripts (7.2% IS, e15a2). Imatinib was initiated and after 3 months CCyR and MMR were achieved. Due to an increasing platelet count one year later, a trephine biopsy was performed that was compatible with ET. Hydroxyurea (HU) was added to treatment. No JAK2V617F mutation was detected. Fifteen years after the initial presentation, a CALR exon 9 mutation was retrospectively detected in all available samples since diagnosis of CML. The mutant allele burden has remained stable during follow-up, while patient being in MR4 with regard to CML. A 50 yr old woman was diagnosed with PV in 1998. Cytogenetic studies were normal and BCR-ABL was undetectable. JAK2V617F homozygous mutation was present on retrospective testing. A complete hematologic remission was achieved with phlebotomy and HU. Ten years later, re-evaluation due to an increasing WBC disclosed the presence of Ph1 chromosome in 20/20 metaphases and BCR-ABL transcripts (38.4% IS, e15a2). Interestingly, JAK2V617F was not detected. After 4 months of treatment with TKI plus HU, a 2-log BCR-ABL reduction was noted, while JAK2V617F was detected again at a heterozygous state. She received sequentially all 3 first available TKIs due to intolerance. Upon TKI treatment for 9 months, CCyR and MMR were achieved in parallel with emergence of JAK2V617F homozygosity. After achieving MR4 for more than 2 years, the TKI was discontinued and, 3 months later, the patient remains in MR4 with persistent JAK2V617F homozygosity. Due to splenomegaly and increased Hct, treatment with HU is continuously required. An 80 yr old female was diagnosed with chronic phase CML [Ph1+, BCR-ABL (35.5% IS, e15a2)]. She achieved mCyR and 1-log reduction of BCR-ABL levels after 6 months on imatinib. Due to imatinib failure, she was switched to nilotinib at 9 months. Two years after initial diagnosis, while CML was in MMR, an increase in Hct and platelets was noticed and JAK2V617F heterozygosity was detected. Retrospective analysis did not reveal JAK2V617F mutation at diagnosis and on the 3-month sample, while low level of mutant V617F allele was detected on the 6-month sample. Increasing levels of mutant versus wild type allele were detected in all subsequent samples. The patient was treated with phlebotomy, HU and ASA in addition to nilotinib. She died 4 years after initial diagnosis from an unrelated cause while in MR4 for CML and complete hematologic remission for PV. Despite these cases seem to be uncommon, they raise intriguing issues regarding the clonal origins of distinct molecular types of MPNs present in the same patient. They may also challenge the traditional hypothesis of evolution of one type of MPN to another. Instead of perceiving clinical and genetic features of second MPN as simple evolution of a precedent MPN, our cases suggest an alternative explanation based on pre-existence of two different MPN clones. Treatment for the initial MPN, especially with highly-efficient targeted agents (like TKIs for Ph+ CML) may facilitate the emergence of a second clone and vice versa. In conclusion, any divergent manifestations in a patient with MPN may warrant further investigation of genetic markers suggestive of an additional MPN entity. A high level of suspicion for the possibility of coexistence Ph+ and Ph- MPN may result in a more comprehensive treatment approach and optimal outcome. Disclosures No relevant conflicts of interest to declare.