Non-radiographic axial spondyloarthritis in South America. Burden of disease and differential features with respect to ankylosing spondylitis at time of diagnosis. A comprehensive analysis with a focus on images.

BACKGROUND: Non-radiographic axial spondyloarthritis (nr-axSpA) data from South America are scarce, especially regarding image features. Objective To estimate the frequency of nr-axSpA and ankylosing spondylitis (AS) in a cohort of Argentinian patients with chronic low back pain (LBP) and to analyze the difference between both, with focus on magnetic resonance imaging (MRI) lesions, at diagnosis. METHODS: Patients with LBP and a diagnosis of axSpA who participated in a reuma-check program were included. All patients with a suspicion of SpA were evaluated using blood analytics, HLA-B27, and images (MRI). Sociodemographic data, SpA features, diagnostic dela,y and clinimetrics were assessed by an operator who was blinded to the patient's test results. On MRI, the presence of SpA lesions was assessed and a concordance exercise was carried out between rheumatologists and radiologist. RESULT: Of 198 LBP patients, 97 had axSpA, 54% of whom were nr-axSpA. A positive MRI was found in 50%. No difference in terms of disease activity, functional impact, laboratory or treatments between nr-axSpA and AS were found. Higher frequencies of male sex and chronic lesions on sacroiliac MRI were found in AS patients. In the logistic regression, an independent association with AS diagnosis was found: male (odds ratio [OR] 4.8), MRI fat replacement (OR 4.6), MRI sclerosis (OR 7.6), and diagnostic delay of more than 2 years (OR 10). The concordance between rheumatologists and radiologists was considered good to very good (κ 0.7-0.8). CONCLUSION: The frequency of nr-axSpA was 54%. We found a higher frequency of being male, more SpA features, and a longer diagnostic delay in patients with AS. Patients with AS had more structural lesions, with a good concordance between rheumatologist and radiologist.

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.