Presentation and Real-World Management of Giant Cell Arteritis (Artemis Study)

Background: Few studies of daily practice for patients with giant cell arteritis (GCA) are available. This French study aimed to describe the characteristics and management of GCA in a real-life setting.Methods: Cross-sectional, non-interventional, multicenter study of patients ≥50 years old who consulted hospital-based specialists for GCA and were under treatment. Patient characteristics and journey, diagnostic methods and treatments were collected. Descriptive analyses were performed.Results: In total, 306 patients (67% females, mean age 74 ± 8 years old) were recruited by 69 physicians (internists: 85%, rheumatologists: 15%); 13% of patients had newly diagnosed GCA (diagnosis-to-visit interval <6 weeks). Overall median disease duration was 13 months (interquartile range 5–26). Most patients were referred by general practitioners (56%), then ophthalmologists (10%) and neurologists (7%). Most common comorbidities were hypertension (46%), psychiatric disorders (10%), dyslipidemia (12%), diabetes (9%), and osteoporosis (6%). Initial GCA presentations included cranial symptoms (89%), constitutional symptoms (74%), polymyalgia rheumatica (48%), and/or other extra-cranial manifestations (35%). Overall, 85, 31, 26, and 30% of patients underwent temporal artery biopsy, high-resolution temporal artery Doppler ultrasonography, 18FDG-PET, and aortic angio-CT, respectively. All patients received glucocorticoids, which were ongoing for 89%; 29% also received adjunct medication(s) (methotrexate: 19%, tocilizumab: 15%). A total of 40% had relapse(s); the median time to the first relapse was 10 months. Also, 37% had comorbidity(ies) related to or aggravated by glucocorticoids therapy.Conclusion: This large observational study provides insight into current medical practices for GCA. More than one third of patients had comorbidities related to glucocorticoid therapy for a median disease duration of 13 months. Methotrexate and tocilizumab were the most common adjunct medications.

Can anticarbamylated protein antibodies be used to support the diagnosis of systemic lupus erythematosus?

Aim: Autoantibody development plays an important role in the pathogenesis of systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). In this study, we aimed to determine the diagnostic value of anticarbamylated protein antibody (anti-CarP) antibody in SLE and RA patients and its relationship with disease prognosis. Material & method: Fifty-seven SLE patients (F/M 50/7; median age 40.9 ± 13.7; median disease duration 2 years) who met the 2012 SLICC SLE diagnostic criteria were included in the study. A total of 46 RA patients selected according to the 2010 ACR/EULAR diagnostic criteria (F/M 38/8; median age 54.2 ± 12.4; median disease duration 2 years) were included. A total of 30 healthy individuals were selected as the control group. The anti-CarP antibody was studied by using human anticarbamylated protein antibody ELISA Kit (SunRedBio, Shanghai, China). Results: Anti-CarP antibody positivity was found to be 17.4% in RA patients (p < 0.001), 54.4% in SLE patients (p < 0.001) and 3.3% in the healthy control group. The anti-CarP antibody was determined to predict SLE patients with 54.4% sensitivity and 96.7% specificity compared with the healthy control group (area under the curve: 0.755; p < 0.001). Conclusion: Anti-CarP antibody positivity was significantly higher in the SLE patients compared with the healthy control and RA group. It has significant sensitivity and specificity in both SLE and RA patients compared with the healthy controls.

AB0726 BIOLOGICS IN CHILDREN WITH IDIOPATHIC INFLAMMATORY MYOPATHIES: AN EXPERIENCE OF SINGLE CENTER

Background:Juvenile dermatomyositis (JDM) is the most common idiopathic inflammatory myopathy (IIM) of childhood, but the involvement of muscle also can be complication of systemic lupus erythematosus (SLE), mixed connective tissue disease (MCTD) and different overlap syndromes. The presence of myopathy can significantly affect the prognosis of the disease and the quality of life. Despite of the absence of official indication for biological therapy fo IIM, it`s may be needed in severe course of disease.Objectives:To analyze in retrospective study the efficacy and safety of Biologics (B) in patients (pts) with IIM in our pediatric rheumatology center.Methods:The study included all pts with rheumatic diseases (RD), who had IIM and received B during past 10 years.Results:A total of 17 pts (10 females) were identified: 23.5% with JDM, 11.8% - SLE, 35.3% - MCTD, 29.4% - overlap syndromes. The median age at the onset of RD was 9.75 years [interquartile range (IQR) 6.9; 13.5]. The median disease duration at the onset of myopathy was 7.0 months [3.0; 10.0], in all pts with JDM – at onset. All pts had myopathic syndrome. The rash tipical for JDM was in 8 pts (47%). The lung involvement observed in 6 pts (35.3%). Levels of serum muscle enzymes (CK, ALT, AST and lactate dehydrogenase [LDH]) were elevated in 88.2% of pts: CK in 52.9% (mean ± std 624.35±1007.2 U/L), ALT – 82.4% (mean ± std 142.18±148.16U/L), AST – 82.4% (mean ± std 159.6±201.1 U/L), LDH – 88.2% (mean ± std 492.5±229.2 U/L). Abnormal EMG findings were in 10 pts (59.4%). Nailfold capillaroscopic changes tipical for IIM had 10 pts (59.4%). Before B 94.1% of pts received corticosteroids (CS), 58.8% - methotrexate, 29.4% - hydroxychloroquine, 17.6% - cyclophosphamide, 11.8% - cyclosporine, 5.9% - mycophenolate mofetil, 5.9% - azathioprine, 47% - IVIG. B therapy was started due to insufficient efficacy of previous therapy. The median age at start of B was 12.3 years [IQR 9.5; 15.0]. The median disease duration prior to treatment with B was 2.25 years [IQR 0,8; 3.6]. 58.8% of pts received rituximab (RTX), 41.2% - abatacept (ABA). The median time between each course of RTX was 182 days [IQR 156–315]. 80% of pts underwent more than one course of RTM therapy, with a maximum of 5 courses. The median duration of ABA therapy was 2.8 years [IQR 1.6; 5.0]. Discontinuation of B due to serious AE was observed in 1 patient with overlap syndrome (5.9%) – macrophage activation syndrome (MAS) 8 day after RTX infusion (5th course, 1st infusion). One patient (female, 12.3 yo) died from MAS (at onset of SLE, developed before B), the others achieved remission. B therapy allowed to reduce the dose of CS to maintenance in all pts, decrease of calcinosis in 2 pts and improve the quality of life.Conclusion:Our study demonstrated that B is highly effective in children with IIM and have the acceptable safety. Early diagnosis and initiation of intensive therapy are important in reducing symptoms of myopathy in RD. It seems that the development of IIM in other RDs, not JDM, indicates the need for B and its good efficacy. The further extended studies are needed.Disclosure of Interests:None declared

AB0234 SURVIVAL OF ABATACEPT IN RHEUMATOID ARTHRITIS PATIENTS: A REAL-LIFE STUDY

Background:Abatacept (ABA) is a biological drug approved for the treatment of rheumatoid arthritis (RA) patients that, by working on CTLA4, can inhibit T-cell activation. Randomized controlled trials have demonstrated both the efficacy and a good safety profile, characterized by a lower infectious risk in comparison with other biological DMARDs, in RA patients. In a real-life setting, the drug retention rate could be considered as a surrogate of drug effectiveness. Data from the literature reported a retention rate of ABA ranging from 55 to 76% at 12 months and from 54 to 64% at 24 months (1-3).Objectives:In the present longitudinal analysis, we evaluated the retention rate of ABA in a large monocentric RA cohort.Methods:We enrolled consecutive RA patients starting treatment with intravenous (IV) or subcutaneous (SC) ABA according to the standard of care. All the patients fulfilled the 2010 ACR/EULAR classification criteria for RA. For each patient, we collected demographic parameters, serological status, previous and concomitant treatments, and disease activity by DAS28 with C reactive protein (DAS28-CRP). All the patients were assessed at baseline, and after 4 and 12 months (T4 and T12, respectively). The reasons for withdrawal of treatment were registered and classified as primary or secondary inefficacy or adverse events (AEs). Kaplan-Meier statistical analysis has been done to evaluate the survival of the treatment in patients with at least 12 months follow-up.Results:We evaluated 161 patients [M/F 21/140; median age 67 years (IQR 21.7), median disease duration 180 months (IQR 161)]. RF was positive in 70.3% of patients, ACPA in 66.4%. ABA was the first biological DMARD in 66 patients (41%). At baseline, the median DAS28-CRP was 4.3 (IQR 1.6) and ABA was administered in association with MTX in 96 patients (59.6%). One hundred-eleven patients (68.9%) started SC ABA [M/F 16/95; median age 64.5 years (IQR 21.5), median disease duration 156 months (IQR 132)], the remaining 50 IV ABA [M/F 5/45, median age 71 years (IQR 60.2), median disease duration 187 months (IQR 157)]. Median age and disease duration were significantly higher in patients receiving IV in comparison with SC ABA (p=0.008 and p=0.03, respectively). We found a significant reduction of DAS28-CRP values during the follow-up in comparison with baseline [4 months: median 3.5 (IQR 1.9), p<0.0001; 12 months: median 3.2 (IQR 1.4), p<0.0001]. Seven patients were lost to follow-up, in the remaining 154 patients a median treatment duration of 33 months (IQR 49) was registered. Data on drug survival are reported in Figure 1A: at 12 months, 92% of patients persisted on treatment; this percentage decreased to 78.2% at 24 months and to 67.9% at 36 months. Furthermore, we did not find any differences in drug survival either with respect to SC vs IV administration (12 months: 93.7% versus 88.6%; 24 months 78.9% versus 72.6%; 36 months 63.7% versus 72.6%; Figure 1B) or according to the association with MTX. Concerning the withdrawal reasons, 46 patients (29.9%) stopped ABA due to inefficacy (primary in 28, secondary in 18), 11 patients (7.1%) due to AEs, and 7 for inadequate adherence (4.5%). Finally, 10 patients switched from IV to SC administration, due to patient’s preference.Conclusion:In our monocentric RA cohort, we have observed a high retention rate of ABA at both 12 and 24 months, confirming the good profile of this drug in terms of effectiveness and safety, irrespective of the route of administration and association with MTX.References:[1]Cagnotto, Arthritis Res Ther 2020; (2) Salmon, J Clin Med 2020; Westhovens, Rheumatol Int 2020.Acknowledgements:I would like to acknowledge Dr. F. Ceccarelli, for her patience.Disclosure of Interests:None declared

AB0464 DRUG SURVIVAL OF TNFi AND SECUKINUMAB IN AXIAL SPONDYLARTHRITIS: A REAL-WORLD MULTICENTRIC COHORT OF 370 PATIENTS

Background:IL17 inhibitors (IL17i) are an alternative for patients with axial spondyloarthritis (axSpA) who did not respond to TNF inhibitors (TNFi). Secukinumab (SEC) is the first human monoclonal antibody that binds to the protein interleukin-17A.Objectives:The objectives of this study were to describe the characteristics of axSpA patients treated with IL17i and TNFi and to assess the persistence with IL17i and TNFi in a real world cohort.Methods:A retrospective multicenter observational study was conducted. axSpA patients (pts) according to ASAS criteria initiating a IL17i or TNFi between June 2016 and December 2019 were included. Demographic features, current and previous use of biologic Disease-modifying antirheumatic drugs (bDMARDs) were collected. Date and reasons of discontinuation – i.e., lack of efficacy, safety issue, sustained remission or others – were collected. Kaplan-Meyer analysis were performed.Results:370 pts were included. Among the 202 patients who received TNFi, 90 (44.6%) were female, mean age was 43.2 +/- 13.2 years, mean body mass index was 26.1 kg/m2 +/- 5.4, 49 pts (46.7%) were smokers. The most common SpA phenotype was axial radiographic (n = 89, 54,9%) and 114 (68.3%) pts were HLA B27 positive, mean BASDAI was 57.5 +/- 14.6, median disease duration was 8.6 years [3.0-10.5]. Among the 168 patients who received SEC, 78 (46.4%) were female, mean age was 47.7 +/- 11.8 years, mean body mass index was 27.2 kg/m2 +/- 5.8, 45 pts (44.1%) were smokers. The most common SpA phenotype was axial radiographic (n = 106, 76,3%) and 114 (78.1%) pts were HLA B27 positive, mean BASDAI was 62.8 +/- 14.8, median disease duration was 9 years [5.0-19.0]. TNFi was the first line bDMARD in 116/202 pts (57.4%) and SEC was the first line bDMARD in 15/168 pts (8.9%). SEC was prescribed at 150mg every month in 121/168 (73.3%) pts. The median persistence with TNFi and SEC were 18.0 months [11.0-27.0] and 12.0 months [6.0-22.0], respectively. During the 3-year follow-up, 130 pts (42 with TNFi and 88 with SEC) discontinued treatment: 80 (22 with TNFi and 58 with SEC) for lack of effectiveness, 41 (16 with TNFi and 25 with SEC) for adverse events. No patient treated with SEC presented a new-onset inflammatory bowel disease.Figure 1.Persistence with SEC after 3 years of follow-upConclusion:In this real world cohort of AxSpA pts, SEC was mostly prescribed at second and third-line, contrary to axSpA pts treated with TNFi. Most reason of discontinuation were related to lack of effectiveness with both therapeutic classes.Disclosure of Interests:Thibaut DELEPINE: None declared., Peggy Philippe Speakers bureau: Abbvie, MSD, Fresenius, Pfizer, UCB Pharma, Novartis, Consultant of: Abbvie, MSD, Fresenius, Pfizer, UCB Pharma, Novartis, Emeline Cailliau: None declared., Eric Houvenagel: None declared., Xavier Deprez Speakers bureau: Pfizer, UCB, Abbvie, Novartis, MSD, Consultant of: Pfizer, UCB, René-Marc Flipo Speakers bureau: Novartis, Lilly, Abbvie, Pfizer, MSD, Consultant of: Novartis, Lilly, Abbvie, Pfizer, MSD, Jean-Guillaume Letarouilly Grant/research support from: Pfizer (research grant).

Joint involvement influences quality of life in systemic lupus erythematosus patients

Introduction Joint involvement represents the major determinant in quality of life (QoL)in Systemic Lupus Erhytematosus (SLE) patients. However, QoLhas been generally evaluated by non-specific questionnaires. We evaluated the relationship between SLE musculoskeletal manifestations and QoL, assessed by LupusQoL. Methods Patients with joint involvement (group A) were compared with those without this feature (group B). Disease activity was assessed by SLEDAI-2k in the whole population, while DAS28 and swollen to tender ratio were applied to assess joint activity. LupusQoL was administered to all the patients. Results Group A included 110 patients [M/F 8/102; median age 49 years (IQR 13), median disease duration 156 months (IQR 216)], group B 58 [M/F 11/47; median age 40 years (IQR 15), median disease duration 84 months (IQR 108)].We found significanlty lower values in all the LupusQoL domains except for one (burden to others) in group A in comparison with group B. A significant correlation between DAS28 values and all the LupusQoL domains in group A was found; only three domains correlated with SLEDAI-2k. Conclusions SLE-related joint involvement significantly influences disease-specific QoL. DAS28 better correlated with LupusQoL domains in comparison with SLEDAI-2k, confirming the need for specific musculoskeletal activity indices.

Comparison of differences in bone microarchitecture in adult- versus juvenile-onset type 1 diabetes Asian males versus non-diabetes males: an observational cross-sectional pilot study

Purpose Evidence about bone microarchitecture in Asian type 1 diabetes (T1D) patients is lacking. We assessed the bone microarchitecture in T1D patients versus controls and compare the differences between juvenile-onset and adult-onset T1D patients. Methods This cross-sectional study recruited 32 Asian males with T1D and 32 age-, sex-, and body mass index (BMI)-matched controls. Dual-energy X-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) for ultradistal nondominant radius and tibia were performed. The data were analyzed using Student’s t test and analysis of covariance. Results Among the patients, 15 had juvenile-onset T1D, with a median disease duration of 11 years, and 17 had adult-onset T1D, with a median disease duration of 7 years. At the radius, adult-onset and juvenile-onset T1D patients had lower total volumetric bone mineral density (vBMD), trabecular vBMD, trabecular bone volume fraction (BV/TV), and trabecular thickness (Tb.Th) (p < 0.05) than the control subjects. After adjusting for BMI, disease duration, and insulin dose, juvenile-onset patients tended to have lower trabecular vBMD, BV/TV, Tb.Th, and intracortical porosity (Ct.Po) than adult-onset patients. At the tibia, adult-onset patients displayed lower total vBMD, lower Ct. vBMD, and higher Ct.Po (p < 0.05), while juvenile-onset patients had lower Tb.Th and standard deviation of trabecular number (1/Tb.N.SD) (p < 0.05) than control subjects. After adjustment for covariates, adult-onset patients tended to have higher cortical pore diameter (Ct.Po.Dm) than juvenile-onset patients. Conclusions T1D patients were associated with compromised bone microarchitecture, adult-onset and juvenile-onset T1D patients demonstrated some differences in cortical and trabecular microarchitecture.

FRI0627-HPR COGNITIVE DISORDERS IN SYSTEMIC LUPUS ERYTHEMATOSUS WITH JUVENILE-ONSET: ONE SINGLE CENTER EXPERIENCE

Background:Juvenile-onset SLE (jSLE) is a more aggressive disease than in adults due to several reasons including cognitive dysfunction, significantly affected the compliance and social rehabilitation of patients (pts).Objectives:To analyze the cognitive, emotional and communicative status of pts with jSLE.Methods:The study included 31 pts (90.3% girls) with jSLE, verified in accordance to SLICC criteria 2012. All pts underwent standard examination in accordance with the diagnosis; in case of suspected neuropsychiatric disorders pts were examined by a neurologist, psychiatrist. Classifying of neuropsychiatric disorders was performed in accordance with the recommendations of the ACR,1999. SLEDAI 2К was used for disease activity assessment. All pts were examined by a clinical psychologist using the standard pathodiagnostic testing.Results:The median age at the onset was 12.0 y.o. [10.6;14.5]. The median disease duration at the time of diagnosis - 0.75 ys [0.5;2.1]. 35.5% pts had neuropsychic disorders at the onset: psychoses – 12.9%, headaches – 12.9%, cognitive disorders – 19.4%, mood disorders – 16.1%, distal polyneuropathy – 12.9%. MRI of the brain was performed in 15 pts: CNS vasculitis was diagnosed in 3 pts (2 – with psychosis, 1 – with cognitive impairment). Median disease activity by SLEDAI at the time of diagnosis was 15 scores [10;23].At the time of examination by the clinical psychologist, the median age of pts was 15.2 ys [12.9;16.5]. The median disease duration was 1.1 ys [0.6;3.8]. Cognitive disorders were detected in 96.8% of the pts. The auditory-speech short-term memory was distributed between the medium and high levels (54.8% and 45.2%, respectively), and the high level of memorization prevailed in the long-term memory (67.7% high, 32.3% medium). A high level of indirect memory was revealed in 67.8% of pts, medium - in 25.8%, and low - in 6.4%. Distribution of the difficulties of attention were identified (64.5% - uneven distribution, 35.5% - sufficient distribution), as well as increased attrition of attention (74.2% - attrition is detected, 25.8% - no attrition). 58.1% of pts demonstrated a high level of inclusion into work, 41.9% - a low one. Concentration of attention was recognized as sufficient in 87.1% of pts, insufficient in 12.9%. The effectiveness of attention was rated as good in 87.1%, decreased – in 12.9%; stability is sufficient - in 64.5%, low - in 35.5%. In the operational side of thinking, a decrease in the level of generalization was revealed (48.4%); there were no disturbances in the motivational component, lability of thinking in the dynamic (12.9%). Various neurotic fears are characteristic for 54.8% of pts; the level of personal anxiety was increased in 41.9%, moderate - in 48.4%, low - in 9.7%. Signs of aggression were revealed in 19.4% of pts, a decrease in the level of social adaptation - in 51.6%. Communication difficulties experienced 83.9% of pts. According to the results of the clinical conversation, attention was focused on availability of conflict situations with peers in the disease onset in 38.7% of pts.Conclusion:Cognitive disorders were detected in the majority of pts with jSLE, regardless of the presence of neuropsychiatric disorders at the onset. The revealed features of the clinical and psychological status of pts with jSLE must be considered when working out an individual rehabilitation model and develop psycho-correctional programs.Disclosure of Interests:None declared

OP0266-HPR WORK PRODUCTIVITY IN PATIENTS WITH AXIAL AND PERIPHERAL SPONDYLOARTHRITIS

Background:Work disability is an important outcome in the treatment of Spondyloarthritis (SpA) since this disease affects people in the most productive stage of life.Objectives:The aim of this study is to investigate the working status and the factors associated with work productivity loss (WPL) in patients with axial (axSpA) and peripheral SpA (pSpA).Methods:Patients with SpA according to ASAS criteria were included consecutively in this multicentric cross-sectional study. Evaluation of activity through a visual analogue scale (0-100), enthesitis (LEI), functional capacity (HAQ and BASFI), disease activity (DAS28 and BASDAI), health status (ASAS Health Index) and quality of life (ASQoL) were calculated. The Ankylosing Spondylitis Disease Activity Score (ASDAS) was recorded. The Work Productivity and Activity Impairment Spondyloarthritis (WPAI SpA) questionnaire was used to assess work productivity.Spearman’s correlation coefficient (ρ) was used to assess the correlation with the percentage of WPL.Results:274 patients with SpA were recruited, 129 (47.1%) with axSpA and 145 (52.9%) with pSpA. 56.6% were women and 33.2% stopped working due to the underlying disease.Among axSpA patients, 70% were radiographic and 30% non radiographic, mean age 45.5 (SD14) yrs, median disease duration 72 (IQR 36-144) months and diagnosis delay 20 (IQR 11-70) months. 45.7% were employed, median hours worked in the last week was 40 (IQR 25-45), median scores for absenteeism was 0% (IQR 0-2), presenteeism 30% (IQR 5-40), WPL 30% (IQR 10-52.5) and activity impairment 30% (IQR 10-50). A positive correlation was found between WPL and the following variables: HAQ (ρ:0.40, p<0.001), BASDAI (ρ:0.48, p<0.001), ASDAS (ρ:0.46, p<0.001), BASFI (ρ:0.59, p<0.001), ASQoL (ρ:0.60, p<0.0001), LEI (ρ:0.31, p:0.02) and ASAS health index (ρ:0.54, p<0.001).Among pSpA patients, mean age was 52.3 (SD13) yrs, median disease duration 60 (IQR 14-120) months and diagnosis delay 12 (IQR 3-24) months. 46.9% were employed, median hrs worked in the last week was 30 (IQR 14-40), absenteeism 0% (IQR 0-7), presenteeism 30% (IQR 2.5-58), WPL 30% (IQR 5-52) and activity impairment 20% (IQR 0-40). A positive correlation was found between WPL and: HAQ (ρ:0.49, p<0.001), ASDAS (ρ:0.58, p<0.001), ASQoL (ρ:0.57, p<0.0001), DAS28 (ρ:0.50, p<0.001), LEI (ρ:0.36, p:0.04) and ASAS health index (ρ:0.52, p<0.001). No statistically significant differences were found in absenteeism, presenteeism, WPL and activity impairment between axSpA and pSpA.Conclusion:Our study showed that WPL in this national cohort was 30% in both groups of patients and is associated with disease activity, enthesitis, health status, quality of life and functional ability.Disclosure of Interests:None declared

Heterogeneous JAK2V617F Allele Burden in Essential Thrombocytosis: Gender and Clinical Correlates.

Essential thrombocytosis (ET) is the most heterogeneous of the chronic myeloproliferative disorders (MPD) when assessed by clonality assays, PRV-1, Mpl expression and JAK2V617F status. The purpose of this study was to prospectively analyze a cohort of 68 ET patients to determine the relationship of quantitative JAK2V617F allele percentage to disease features. The cohort consisted of 18 men and 50 women followed at our institution with a median disease duration of 7 years (range 1–24 years); all patients were clinically assessed between 2005 and 2006. Neutrophil genomic DNA and platelet cDNA were prepared from blood samples obtained at the time of clinical assessment and quantitative JAK2V617F measurements were made using a sensitive allele-specific, quantitative PCR assay. Median patient age at diagnosis was 47 years (range 2–84) without gender difference. JAK2V617F-positive patients were older than patients without the mutation (57 versus 41 years, p=<0.001). When assessed by neutrophil genomic DNA, more male than female ET patients were JAK2V617F-positive (56% versus 36%); however, when assessed by platelet cDNA, males and females had a similar JAK2V617F prevalence (60% versus 73%). JAK2V617F-positive male ET patients also had a higher median neutrophil allele percentage than JAK2V617F-positive female patients (47%, range 17–63, versus 31%, range 5–64). In 25 ET patients (15 female and 10 male), simultaneous JAK2V617F allele assessment in neutrophils and platelets identified 4 patients, all female, who were JAK2V617F-positive only in their platelet cDNA. JAK2V617F status did not correlate with the prevalence of erythromelalgia (4/11 JAK2V617F-positive), transient ischemic attack (3/7 JAK2V617F-positive), stroke (1/4 JAK2V617F-positive), migraine (7/18 JAK2V617F-positive), acute coronary syndromes (2/6 JAKV617F-positive), deep venous thrombosis (0/1 JAK2V617F-positive), peripheral arterial thrombosis (1/2 JAKV617F-positive), or hydroxyurea, interferon or anagrelide use. When controlled for gender, there were no significant differences in leukocyte count, hemoglobin concentration, reticulocyte count or platelet count between JAK2V617F-positive and -negative individuals. JAK2V617F status did not correlate with a family history of an MPD, present in 6 JAK2V617F-negative patients (3 male, 3 female) and 9 JAK2V617F-positive patients (2 male, 7 female). During the study period, phenotypic conversion occurred in 5 patients with a median disease duration of 10 years (range 3–20 years); 3 converted to polycythemia vera (2/3 JAK2V617F positive) and 2 to idiopathic myelofibrosis (both JAK2V617F-positive). In those patients with phenotypic conversion (3 men and 2 women), the JAK2V617F allele percentages either increased to or were at the upper end of the cohort JAK2V617F allele percentage distribution. In summary, in a well-defined, prospectively studied ET patient population, the neutrophil JAK2V617F allele burden was higher in men than women and in some women, JAK2V617F expression was restricted to platelets alone. While phenotypic conversion was associated with an increasing or high JAK2V617F allele percentage, neutrophil JAK2V617F did not correlate with platelet-mediated micro- or macrovascular events nor was there any correlation with hemoglobin, white cell count or platelet count. We conclude that JAK2V617F allele burden in ET is gender-specific and that comparison of JAK2V617F-positive and -negative ET patients must consider both neutrophil and platelet quantitative JAK2V617F allele expression.