Power Doppler signal at the enthesis and bone erosions are the most discriminative OMERACT ultrasound lesions for SpA: results from the DEUS (Defining Enthesitis on Ultrasound in Spondyloarthritis) multicentre study.

OBJECTIVES: To assess, in spondyloarthritis (SpA), the discriminative value of the Outcome Measures in Rheumatology (OMERACT) ultrasound lesions of enthesitis and their associations with clinical features in this population. METHODS: In this multicentre study involving 20 rheumatology centres, clinical and ultrasound examinations of the lower limb large entheses were performed in 413 patients with SpA (axial SpA and psoriatic arthritis) and 282 disease controls (osteoarthritis and fibromyalgia). 'Active enthesitis' was defined as (1) power Doppler (PD) at the enthesis grade ≥1 plus entheseal thickening and/or hypoechoic areas, or (2) PD grade >1 (independent of the presence of entheseal thickening and/or hypoechoic areas). RESULTS: In the univariate analysis, all OMERACT lesions except enthesophytes/calcifications showed a significant association with SpA. PD (OR=8.77, 95% CI 4.40 to 19.20, p<0.001) and bone erosions (OR=4.75, 95% CI 2.43 to 10.10, p<0.001) retained this association in the multivariate analysis. Among the lower limb entheses, only the Achilles tendon was significantly associated with SpA (OR=1.93, 95% CI 1.30 to 2.88, p<0.001) in the multivariate analyses. Active enthesitis showed a significant association with SpA (OR=9.20, 95% CI 4.21 to 23.20, p<0.001), and unlike the individual OMERACT ultrasound lesions it was consistently associated with most clinical measures of SpA disease activity and severity in the regression analyses. CONCLUSIONS: This large multicentre study assessed the value of different ultrasound findings of enthesitis in SpA, identifying the most discriminative ultrasound lesions and entheseal sites for SpA. Ultrasound could differentiate between SpA-related enthesitis and other forms of entheseal pathology (ie, mechanical enthesitis), thus improving the assessment of entheseal involvement in SpA.

Seguridad de las drogas biológicas y sintéticas dirigidas utilizadas en pacientes con enfermedades reumáticas inmunomediadas. Datos del registro BIOBADASAR 3.0 / Safety of biological and targeted synthetic drugs in patients with immune-mediated rheumatic diseases. Data from the BIOBADASAR 3.0 registry

Introducción: conocer la seguridad de las drogas actualmente disponibles para el tratamiento de las enfermedades reumáticas es muy importante al momento de tomar decisiones terapéuticas objetivas e individualizadas en la consulta médica diaria. Asimismo, datos de la vida real amplían el conocimiento revelado por los ensayos clínicos. Objetivos: describir los eventos adversos (EA) reportados, estimar su frecuencia e identificar los factores relacionados con su desarrollo. Materiales y métodos: se utilizaron datos BIOBADASAR, un registro voluntario y prospectivo de seguimiento de EA de tratamientos biológicos y sintéticos dirigidos en pacientes con enfermedades reumáticas inmunomediadas. Los pacientes son seguidos hasta la muerte, pérdida de seguimiento o retiro del consentimiento informado. Para este análisis se extrajeron datos recopilados hasta el 31 de enero de 2023. Resultados: se incluyó un total de 6253 pacientes, los cuales aportaron 9533 ciclos de tratamiento, incluyendo 3647 (38,3%) ciclos sin drogas modificadoras de la enfermedad biológicas y sintéticas dirigidas (DME-b/sd) y 5886 (61,7%) con DME-b/sd. Dentro de estos últimos, los más utilizados fueron los inhibidores de TNF y abatacept. Se reportaron 5890 EA en un total de 2701 tratamientos (844 y 1857 sin y con DME-b/sd, respectivamente), con una incidencia de 53,9 eventos cada 1000 pacientes/año (IC 95% 51,9-55,9). La misma fue mayor en los ciclos con DME-b/sd (71,1 eventos cada 1000 pacientes/año, IC 95% 70,7-77,5 versus 33,7, IC 95% 31,5-36,1; p<0,001). Las infecciones, particularmente las de la vía aérea superior, fueron los EA más frecuentes en ambos grupos. El 10,9% fue serio y el 1,1% provocó la muerte del paciente. El 18,7% de los ciclos con DME-b/sd fue discontinuado a causa de un EA significativamente mayor a lo reportado en el otro grupo (11,5%; p<0,001). En el análisis ajustado, las DME-b/sd se asociaron a mayor riesgo de presentar al menos un EA (HR 1,82, IC 95% 1,64-1,96). De igual manera, la mayor edad, el mayor tiempo de evolución, el antecedente de enfermedad pulmonar obstructiva crónica, el diagnóstico de lupus eritematoso sistémico y el uso de corticoides se asociaron a mayor riesgo de EA. Conclusiones: la incidencia de EA fue significativamente superior durante los ciclos de tratamientos que incluían DME-b/sd.

Introduction: knowing the efficacy and safety of the drugs currently available for the treatment of rheumatic diseases is very important when making objective and individualized therapeutic decisions in daily medical consultation. Likewise, real-life data extends the knowledge revealed by clinical trials. Objectives: to describe the reported adverse events (AEs), estimate their frequency and identify factors associated to them. Materials and methods: BIOBADASAR data were used, which is a voluntary, prospective follow-up registry of AEs of biological and synthetic treatments in patients with immune-mediated rheumatic diseases. Patients are followed until death, loss of followup, or withdrawal of informed consent. To carry out this analysis, the data collected up to January 31, 2023 was extracted. Results: a total of 6253 patients were included, who contributed with 9533 treatment periods, including 3647 (38.3%) periods without b/ts-DMARDs and 5886 (61.7%) with b/ts-DMARDs. Among the latter, the most used were TNF inhibitors and abatacept. A total of 5890 AEs were reported in a total of 2701 treatments (844 and 1857 without and with b/ts-DMARDs, respectively), with an incidence of 53.9 events per 1000 patients/ year (95% CI 51.9-55.9). It was higher during the periods with b/ts-DMARDs (71.1 events per 1000 patients/year, 95% CI 70.7-77.5 vs 33.7, 95% CI 31.5-36.1, p<0.001). Infections, particularly those of the upper respiratory tract, were the most frequent AEs in both groups. 10.9% were severe and 1.1% were associated with the death of the patient. 18.7% of the periods with b/ts-DMARDs were discontinued due to an AE, significantly higher than that reported in the other group (11.5%; p<0.001). In the adjusted analysis, b/ts-DMARDs were associated with a higher risk of presenting at least one AE (HR 1.82, 95% CI 1.64-1.96). Similarly, older age, longer evolution time, history of chronic obstructive pulmonary disease, diagnosis of systemic lupus erythematosus, and use of corticosteroids were associated with a higher risk of AE. Conclusions: the incidence of AEs was significantly higher during those treatment periods that included DME-b/sd.

Characterization of Patients With Dermatomyositis According to Anti-Melanoma Differentiation-Associated Gene-5 Autoantibodies in Centers from 3 Latin American Countries: A Cohort Study.

BACKGROUND/OBJECTIVE: The anti-melanoma differentiation-associated protein 5 (MDA5) autoantibodies have been associated with a high frequency of interstitial lung disease (ILD) and rapidly progressive ILD (RP-ILD) in dermatomyositis (DM) patients, mainly in Asian subjects. However, there is scarce information about these parameters in Latin American patients. METHOD: This was a medical records review cohort study that included classic DM (CDM) and clinically amyopathic DM (CADM) patients from 3 Latin American countries (Argentina, Brazil, and Mexico). RESULTS: A total of 270 DM patients were evaluated: 25.9% with CADM and 74.1% with CDM. The overall prevalence of ILD and RP-ILD, respectively, was 70 (25.9%) and 4 (1.5%) of the 270 patients, and the distributions were comparable between patients with CDM and CADM. The anti-MDA5 was present in 31 (25.4%) of 122 CDM patients and in 17 (48.6%) of 35 CADM patients; it was not associated with presence of ILD and RP-ILD. However, anti-MDA5-positive CDM patients had significantly high frequency of "mechanic's hands," arthralgia, arthritis, and lower serum levels of creatine phosphokinase, whereas anti-MDA5-positive CADM patients had significantly high frequency of arthritis. Pulmonary infection and ILD are main causes of death in DM patients. CONCLUSIONS: In the present study, the prevalence of ILD in DM patients is comparable to that described in the literature, in contrast to the very low frequency of RP-ILD. In addition, the anti-MDA5 is not associated with ILD and RP-ILD, but anti-MDA5-positive DM patients present conditions that mimic antisynthetase syndrome. Pulmonary infection and ILD were the main causes of death in our sample.

Myositis-specific antibodies and clinical characteristics in patients with autoimmune inflammatory myopathies: reported by the Argentine Registry of Inflammatory Myopathies of the Argentine Society of Rheumatology.

INTRODUCTION/OBJECTIVES: To describe clinical features in patients with inflammatory myopathies (IMs) from the Argentine Registry of Inflammatory Myopathies, and their relationship with myositis-specific antibodies (MSAs). METHODS: This cross-sectional study included 360 adult patients with dermatomyositis (DM), polymyositis (PM), and inclusion body myositis. Demographics, clinical, and serological characteristics were retrospectively recorded (2016-2019). MSAs were determined by immunoblotting. Patients who were positive for anti-Jo-1, Mi-2, and MDA5 were compared against a group of patients, taken as reference group, who were negative for all MSAs. RESULTS: Women 72%, median age at diagnosis was 47.3 years (18-82). The most frequent subtypes were DM (43.9%) followed by PM (30%).The most frequent MSAs were anti-Jo-1 (51/317), 16.1%; MDA5 (12/111), 10.8%, and Mi-2 (23/226), 10.2%. Anti-Jo-1 was associated (p < 0.05) with a higher frequency of chronic disease course, interstitial lung disease (ILD), arthritis, and mechanic's hands. Anti-Mi-2 was found in patients who had higher frequency of skin manifestations and higher CK values (p < 0.001). Patients with anti-MDA5 had normal or low CK levels. Anti-MDA5 was associated (p < 0.05) with skin manifestations, arthritis, and ILD. The rest of MSAs had frequencies lower than 8%. Anti-TIF1ϒ was found in eight DM patients and one had cancer. Anti-SRP was found in seven patients who had PM and elevated CK. CONCLUSION: Anti-Jo-1 was the most frequent MSA, and was associated with ILD; MDA5 was associated with CADM and ILD, and Mi-2, with classical DM. Despite the different prevalence with respect to other cohorts, the clinical characteristics for each MSA group were similar to the data reported in other studies. Key Points • This study describes the prevalence of MSAs in the Argentine Registry of IMs. • Anti-Jo-1 and anti-MDA5 were associated with ILD. • Anti-Mi-2 was the third most frequent MSA, associated with classical DM.

Métodos de diagnóstico en el estudio de las Miopatías Inflamatorias Autoinmunes: Datos del Registro Argentino de Miopatías Inflamatorias de la Sociedad Argentina de Reumatología / Diagnostic methods in the study of Inflammatory Myopathies. Data from the Argentine Register: Argentine Rheumatology Society

Las Miopatías Inflamatorias Autoinmunes (MI) comprenden un grupo de enfermedades heterogéneas con presentación y características clínicas variables. Se distinguen subtipos clínicos como Polimiositis (PM), Dermatomiositis (DM), Miositis por cuerpos de Inclusión (MCI), Miopatía Necrotizante Inmunomediada (MNIM), Miositis de los Síndromes de Superposición, formas juveniles de MI (DMJ), Síndrome Antisintetasa (SAS) y Miopatía Asociada a Cáncer (MAC). La presencia de anticuerpos séricos y el infiltrado inflamatorio en la biopsia de músculo sugiere que se trata de una condición autoinmune. Realizar el diagnóstico de las MI suele ser un desafío y las herramientas diagnósticas no siempre están disponibles en la práctica diaria. Se obtuvo información sobre la disponibilidad de estos métodos del Registro Argentino de Miopatías Inflamatorias. El estudio de enzimas musculares, Anticuerpos Antinucleares (ANA), anticuerpo anti-Jo-1 y la tomografía computada de tórax, estuvieron disponibles para la mayoría de los pacientes mientras que la Resonancia Magnética de musculo (RM), el estudio de difusión de monóxido de carbono (DLco) y la biopsia muscular se realizaron en menos del 50% de los casos. La determinación de otros anticuerpos específicos de miositis, de importancia en el diagnóstico y pronóstico de la enfermedad se realizó, en mayor parte, a través de un subsidio de la SAR.

The Idiopathic Inflammatory Myopathies (IIM) comprise a heterogeneous group of acquired muscle diseases classified as polymyositis (PM), dermatomyositis (DM), Inclusion Body Myositis (IBM), Immuno Mediated Necrotizing Myopathies (IMNM), Overlap Myositis (OM), juvenile myositis, Antisynthethase Syndrome (ASS) and cancer related myositis (CAM). The presence of myositis specific antibodies in the serum and autoantibodies against target antigens and inflammatory infiltrates in muscle tissue suggests the autoimmune condition of the disease. The diagnosis of inflammatory myopathies is often a challenge and the disposal of diagnostic tools are not always available in daily practice. Information on the accessibility of these methods was obtained from the Argentine Register of Myopathies. The study of muscle enzymes, ANA, anti-Jo-1 antibodies and chest tomography were easy to get to most patients while muscle MRI, lung diffusion capacity for carbon monoxide (DLco) and muscle biopsy were performed in less than 50% of cases. Other myositis specific antibodies, necessary for disease diagnosis and prognosis, were mostly done through a subsidy from the Argentine Rheumatology Society.

Métodos de diagnóstico en el estudio de las Miopatías Inflamatorias Autoinmunes: Datos del Registro Argentino de Miopatías Inflamatorias de la Sociedad Argentina de Reumatología / Diagnostic methods in the study of myopathies Inflammatory Autoimmune: Data from the Argentine Registry of Inflammatory Myopathies of the Argentine Society of Rheumatology

Las Miopatías Inflamatorias Autoinmunes (MI) comprenden un grupo de enfermedades heterogéneas con presentación y características clínicas variables. Se distinguen subtipos clínicos como Polimiositis (PM), Dermatomiositis (DM), Miositis por cuerpos de Inclusión (MCI), Miopatía Necrotizante Inmunomediada (MNIM), Miositis de los Síndromes de Superposición, formas juveniles de MI (DMJ), Síndrome Antisintetasa (SAS) y Miopatía Asociada a Cáncer (MAC).La presencia de anticuerpos séricos y el infiltrado inflamatorio en la biopsia de músculo sugiere que se trata de una condición autoinmune. Realizar el diagnóstico de las MI suele ser un desafío y las herramientas diagnósticas no siempre están disponibles en la práctica diaria. Se obtuvo información sobre la disponibilidad de estos métodos del Registro Argentino de Miopatías Inflamatorias. El estudio de enzimas musculares, Anticuerpos Antinucleares (ANA), anticuerpo anti-Jo-1 y la tomografía computada de tórax, estuvieron disponibles para la mayoría de los pacientes mientras que la Resonancia Magnética de musculo (RM), el estudio de difusión de monóxido de carbono (DLco) y la biopsia muscular se realizaron en menos del 50% de los casos. La determinación de otros anticuerpos específicos de miositis, de importancia en el diagnóstico y pronóstico de la enfermedad se realizó, en mayor parte, a través de un subsidio de la SAR.

The Idiopathic Inflammatory Myopathies (IIM) comprise a heterogeneous group of acquired muscle diseases classified as polymyositis (PM), dermatomyositis (DM), Inclusion Body Myositis(IBM), ImmunoMediated Necrotizing Myopathies, (IMNM), Overlap Myositis(OM), juvenile myositis, Antisynthethase Syndrome (ASS) and cancer related myositis(CAM).The presence of myositis specific antibodies in the serum and autoantibodies against target antigens and inflammatory infiltrates in muscle tissue suggests the autoimmune condition of the disease. The diagnosis of inflammatory myopathies is often a challenge and the disposal of diagnostic tools are not always available in daily practice. Information on the accessibility of these methods was obtained from the Argentine Register of Myopathies. The study of muscle enzymes, ANA, anti-Jo-1 antibodies and chest tomography were easy to get to most patients while muscle MRI, lung diffusion capacity for carbon monoxide (DLco%) and muscle biopsy were performed in less than 50% of cases. Other myositis specific antibodies, necessary for disease diagnosis and prognosis, were mostly done through a subsidy from the Argentine Rheumatology Society.

Changing rate of serious infections in biologic-exposed rheumatoid arthritis patients. Data from South American registries BIOBADABRASIL and BIOBADASAR.

OBJECTIVE: Most reports on serious infections (SI) in rheumatoid arthritis (RA) patients treated with biological disease-modifying antirheumatic drugs (bDMARDs) are from the USA and Western Europe. Data from other regions are largely missing. We report data from South American countries with different backgrounds and health-care systems but similar registries. METHODS: We merged 2010-2016 data from two registries, BIOBADABRASIL (Brazil) and BIOBADASAR (Argentina), which share the same protocol, online platform and data monitoring process. Patients with active RA were included when they began the first bDMARD or a conventional synthetic DMARD (csDMARD, control group). The SI incidence rate (IR) per 1000 patient/years and adjusted IR ratio (aIRR) were estimated for bDMARDs and csDMARDs. RESULTS: Data were analysed for 3717 RA patients with an exposure of 13,380 patient/years. The 2591 patients treated with bDMARDs (64% tumour necrosis factor-α inhibitors (TNFi)) had a follow-up of 9300 years, and the 1126 treated with csDMARDs had an exposure of 4081 patient/years. The SI IR was 30.54 (CI 27.18-34.30) for all bDMARDs and 5.15 (CI 3.36-7.89) for csDMARDs. The aIRR between the two groups was 2.03 ([1.05, 3.9] p = 0.034) for the first 6 months of treatment but subsequently increased to 8.26 ([4.32, 15.76] p < 0.001). The SI IR for bDMARDs decreased over time in both registries, dropping from 36.59 (28.41-47.12) in 2012 to 7.27 (4.79-11.05) in 2016. CONCLUSION: While SI remains a major concern in South American patients with RA treated with bDMARDs, a favourable trend toward a reduction was observed in the last years.Key Points• New comprehensive data on biologic drugs safety from international collaboration in South America.• First proposal for national registries data merging in South America.• Serious infections remain a major concern in RA patients treated with biologics.• A significant reduction of serious infections in RA patients exposed to biologics was observed over a 7 years period.

Tuberculin test conversion in patients with chronic inflammatory arthritis receiving biological therapy.

OBJECTIVE: The blockade of inflammatory mediators produced by biological therapies is associated with an increased risk of opportunistic infections, as for example Mycobacterium tuberculosis (MT). Given the endemic situation of tuberculosis (TB) in some countries and immunosuppression/anergy of patients with chronic inflammatory arthritis, we wonder whether it is necessary to monitor the MT infection after starting the biological treatment. To evaluate the frequency of the tuberculin skin test (TST) conversion and its association with an active TB infection and other disease variables. METHODS: Patients with rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), and spondyloarthritis (SpA) receiving treatment with anti-TNF, tocilizumab, and/or abatacept agents were included into the study. Patients had to have a negative TST (<5 mm) at the baseline, and a second TST was performed 2-22 months after the initiation of biologic therapy. The TST conversion was considered as a variation ≥5 mm between the two TSTs performed within an interval between 2 months and 2 years. RESULTS: A total of 85 patients were included into the study, and 78.8% were women, with a median schooling duration of 12 years. A total of 74.1% of patients had RA, 16.5% psoriatic arthritis, and 4.7% AIJ and ankylosing spondylitis. Regarding treatment, 75.3% received anti-TNF therapy (31.8% etanercept, 21.2% adalimumab, 17.6% infliximab, 3.5% golimumab, and 1.2% certolizumab), 15.3% tocilizumab, and 9.4% abatacept. Eight patients (9.4%) developed a TST conversion. The shift was more frequent in men (62.5%) than in women (37.5%) (p=0.009), and in those with a prolonged disease duration (X 226±109 vs X130±105 [p=0.017]). This association remained after adjusting for other variables. All patients who developed a TST conversion received prophylactic isoniazid, and only one patient with other risk factors developed active TB. CONCLUSION: The frequency of a TST conversion in patients with chronic inflammatory arthritis was low and was associated with male gender and longer disease duration.

Viraje tuberculínico en pacientes con artritis inflamatorias crónicas y terapia biológica / Tuberculin test conversión in patients with chronic inflammatory arthritis and biological therapy

Introducción: El bloqueo de los mediadores inflamatorios producido por las terapias biológicas se asocia a un aumento de las infecciones oportunistas, como infección por Mycobacterium tuberculosis (MT), por lo que se recomienda realizar intradermorreacción de derivado proteico purificado (PPD) antes de iniciar dicho tratamiento. Teniendo en cuenta la situación endémica de tuberculosis (TBC) en nuestro país y la inmunosupresión/anergia de los pacientes con artritis inflamatorias crónicas, nos planteamos si es necesario monitorear la infección de MT luego de iniciado el tratamiento biológico. Objetivos: Evaluar la frecuencia de viraje de PPD y la asociación del viraje con infección activa por MT u otras variables. Materiales y métodos: Se incluyeron pacientes con Artritis Reumatoidea (AR), Artritis Idiopática Juvenil (AIJ) y Espondiloartritis (EsP) en tratamiento con agentes Anti-TNFα, Tocilizumab y/o Abatacept. Los pacientes debían tener una PPD negativa (<5 mm) basal y una segunda PPD realizada entre los 2 y 22 meses posteriores. Se consignaron datos sociodemográficos (edad, género, estatus social, hacinamiento), antecedentes patológicos (desnutrición, alcoholismo, tuberculosis y sus contactos), tipo de enfermedad reumática y tiempo de evolución, índices de actividad (RAPID-3, BASDAI), de función (BASFI, HAQ-II) y tratamiento concomitante con corticoides (CT), drogas modificadoras de la enfermedad (DME) y terapia biológica (TB). Se consideró viraje de PPD a una variación ≥ a 5 mm entre dos pruebas realizadas con intervalo entre 2 meses y 2 años. En caso de viraje se recomendó seguimiento por Neumonología e Infectología. Análisis estadístico: las variables categóricas se compararon por Chi2 y test exacto de Fisher y las continuas por T-test o Mann-Whitney. Regresión logística múltiple. Resultados: Se incluyeron 85 pacientes, 78,8% eran mujeres, con una escolaridad mediana de 12 años. El 98,8% tenía residencia urbana, 12,9% tenía criterios de hacinamiento y 8,2% ingresos inferiores a la línea de pobreza. 5,9% de los pacientes había padecido TBC con cumplimiento de tratamiento completo y 2,4% reportó contactos con TBC. En cuanto al tipo de artropatía inflamatoria crónica, el 74,1% de los pacientes tenían AR, el 16,5% Artritis Psoriásica (APs) y 4,7% tanto AIJ como Espondilitis Anquilosante. Con respecto al tratamiento, 18,8% recibía más de 10 mg diarios de esteroides orales, el 91,8% DME, (84,7% Metotrexato y 21,2% Leflunomida). El 75,3% recibía terapia Anti-TNFα (31,8% Etanercept, 21,2% Adalimumab, 17,6% Infliximab, 3,5% Golimumab y 1,2% Certolizumab), el 15,3% Tocilizumab y el 9,4% Abatacept. De los 85 pacientes, 8 viraron (9,4%). El viraje fue más frecuente en varones 62,5% vs mujeres 37,5% (p=0,009) y en aquellos con mayor tiempo de evolución de enfermedad en meses [X226±109 vs X130±105 (p=0,017)]. Esta asociación se mantuvo luego de ajustar para otras variables. Todos los pacientes que presentaron viraje recibieron isoniacida (INH) profiláctica y sólo un paciente, con factores de riesgo, desarrolló tuberculosis activa. Conclusión: La frecuencia del viraje tuberculínico en pacientes con artritis inflamatorias crónicas fue baja y se asoció a sexo masculino y mayor tiempo de evolución de la enfermedad

Clinical and immunogenetic characterization in psoriatic arthritis patients.

In psoriatic arthritis (PsA), genetic factors play a substantial role in disease susceptibility as well as in its expression. This study aims to determine the distribution of class I and class II HLA antigens in PsA patients and secondly to analyze the influence of genetic factors in the clinical expression of the disease. Consecutive PsA patients (CASPAR criteria) with less than 1 year of disease duration were included. Sociodemographic and clinical data were recorded. Blood samples were obtained, DNA was extracted by polymerase chain reaction (PCR), and class I (A, B, and C) and class II (DR) HLA antigens were determined by oligotyping. A control group of 100 nonrelated healthy controls from the general population served as control. p values were corrected (pc) according to the number of alleles tested. A total of 73 patients were included, 37 were females (50.7 %) with a median disease duration of 72 months (interquartile range (IQR) 24-149). Thirty-three patients (45.2 %) had a family history of psoriasis. When analyzing all the class I and class II HLA antigens, a significantly higher frequency of B38 (odds ratio (OR) 2.95, p = 0.03) and Cw6 (OR 2.78, p = 0.009) was found in PsA patients compared to the control group. On the contrary, the HLA-A11 (OR 0.14, p = 0.04) and B7 (OR 0.31, p = 0.03) were significantly more frequent among healthy controls. Furthermore, B18 was significantly more frequent in patients with early arthritis onset (less than 40 years): seven patients (22.6 %) with early onset compared to two patients (4.8 %) with late onset (p = 0.03). No association between HLA-B27 and spondylitis or HLA-DR4 with polyarticular involvement was observed. The HLA-B38 and Cw6 alleles are associated with a greater PsA susceptibility in Argentine population.