Uso de PCR digital para definir terapéuticas específicas y seguimiento en enfermedades autoinflamatorias / Use of digital PCR to define specific therapeutics and follow-up in autoinflammatory diseases

Las enfermedades autoinflamatorias (AIDs) son un grupo heterogéneo de desórdenes monogénicos o poligénicos, con características de disregulación inmune innata y/o adaptativa, cuyo mecanismo central es la autoinflamación pero también pueden presentarse con autoinmunidad e inmunodeficiencia. En estos últimos años el desarrollo de las tecnologías de secuenciación masiva han provocado una explosión en el descubrimiento de nuevos genes responsables de AIDs monogénicas. Esto remarca la importancia de implementar este tipo de estudios para llegar a un diagnóstico definitivo sobre todo en este grupo de patologías genéticamente muy diversas donde los fenotipos clínicos se solapan. Sin embargo, dada la presencia de variantes de significación incierta (VUS), los resultados pueden no ser concluyentes planteándose la necesidad de desarrollar pruebas funcionales para determinar la patogenicidad de dichas variantes genéticas. En nuestro grupo de trabajo estamos aplicando la PCR digital en gotas (ddPCR), una técnica cuantitativa de 3era generación altamente sensible, especifica y reproducible que no necesita de curvas de calibración, para desarrollar pruebas funcionales que permitan no sólo reclasificar variantes VUS para lograr diagnósticos definitivos sino también estudiar los mecanismos responsables de las principales AIDs que permitan una estratificación de las terapéuticas especificas a aplicar y de esta manera poder contribuir al diagnóstico, tratamiento y seguimiento de nuestros pacientes en forma personalizada. (AU)

Autoinflammatory diseases (AIDs) are a heterogeneous group of monogenic or polygenic disorders, with characteristics of inborn and/or adaptive immune dysregulation, whose central mechanism is autoinflammation but may also present with autoimmunity and immunodeficiency. In recent years the development of massive sequencing technologies has led to an exponential increase in the discovery of new genes responsible for monogenic AIDs. This emphasizes the importance of the implementation of this type of studies to make a definitive diagnosis, especially in this group of genetically very diverse diseases with overlapping clinical phenotypes. However, given the presence of variants of uncertain significance (VUS), the results may not be conclusive, raising the need to develop functional tests to determine the pathogenicity of these genetic variants. In our working group we are applying droplet digital PCR (ddPCR), a highly sensitive, specific and reproducible third generation quantitative technique that does not require calibration curves, to develop functional tests that allow not only to reclassify VUS variants to achieve definitive diagnoses but also to study the mechanisms responsible for the main AIDs that allow for the stratification of specific treatments to be used and thereby contribute to the individualized diagnosis, treatment, and follow-up of our patients (AU)

Enfermedades autoinflamatorias / Autoinflammatory diseases

Las enfermedades autoinflamatorias monogénicas son desórdenes raros que resultan en defectos del sistema inmune innato, originando excesiva respuesta a señales de peligro, activación espontánea de vías inflamatorias o pérdida de reguladores inhibitorios. En los últimos 15 años un creciente número de enfermedades inflamatorias monogénicas han sido descriptas y sus respectivos genes responsables identificados. Las proteínas codificadas por estos genes están involucradas en las vías regulatorias de la inflamación y están expresadas fundamentalmente en las células del sistema inmune innato. Si bien un grupo de pacientes exhibe inflamación sistémica episódica (fiebres periódicas), estos desórdenes están mediados por una continua sobreproducción y liberación de mediadores pro-inflamatorios -especialmente la interleucina 1beta- y su conceptualización como enfermedades autoinflamatorias es preferible por sobre la de fiebres periódicas. Las enfermedades más frecuentes son fiebre mediterránea familiar (FMF), TRAPS, deficiencia de mevalonatocinasa/síndrome de hiper IgD (MKD/HIDS) y los síndromes periódicos asociados a criopirina (CAPS). Sus características clínicas frecuentemente incluyen fiebre, erupciones cutáneas, compromiso de serosas y reactantes de fase aguda. Los autoanticuerpos están usualmente ausentes pero pueden observarse en ciertos síndromes. El diagnóstico es clínico y se basa en las características fenotípicas. El diagnóstico genético es muy importante pero debe ser realizado de manera juiciosa e interpretado con cautela. El tratamiento con agentes biológicos que bloquean citocinas pro-inflamatorias, particularmente IL-1, ha demostrado ser efectivo en muchos pacientes. Sin embargo, en otros tantos casos no se descubren anormalidades genéticas y el tratamiento es subóptimo, planteando la posibilidad de mutaciones patogénicas en genes y vías aún no explorados.

The monogenic autoinflammatory diseases are rare, genetic disorders resulting in constitutive innate immune defects leading to excessive response to danger signals, spontaneous activation of inflammatory mediators or loss of inhibitory regulators. During the past 15 years, a growing number of monogenic inflammatory diseases have been described and their respective responsible genes identified. The proteins encoded by these genes are involved in the regulatory pathways of inflammation and are mostly expressed in cells of the innate immune system. Although a group of patients exhibit episodic systemic inflammation (periodic fevers), these disorders are mediated by continuous overproduction and release of pro-inflammatory mediators, notably IL-1β, and are best considered as autoinflammatory diseases rather than periodic fevers. The most common autoinflammatory diseases are familial Mediterranean fever (FMF), TNF receptor-associated periodic syndrome (TRAPS), mevalonate kinase deficiency/hyperimmunoglobulin D syndrome (MKD/HIDS) and the cryopyrin-associated periodic syndromes (CAPS). Clinical features often include fever, cutaneous rash, serosal involvement and acute phase reactants. Autoantibodies are usually absent but may accompany certain syndromes. Diagnosis remains clinical and is based on the different phenotypic features. Genetic diagnosis is of utmost importance, but must be performed judiciously and interpreted cautiously. Treatment with biologic agents that block proinflammatory cytokines, particularly IL-1, has proved to be dramatically effective in many patients. Still, in many cases of autoinflammation no genetic abnormalities are detected and treatment remains suboptimal, raising the question of novel pathogenic mutations in unexplored genes and pathways.

Síndromes autoinflamatórias hereditárias na faixa etária pediátrica / Pediatric hereditary autoinflammatory syndromes

OBJETIVO: Descrever as principais síndromes autoinflamatórias hereditárias na faixa etária pediátrica. FONTES DOS DADOS: Foi realizada uma revisão da literatura nas bases de dados PubMed e SciELO, utilizando as palavras-chave "síndromes autoinflamatórias” e "criança”, e incluindo referências bibliográficas relevantes. SÍNTESE DOS DADOS: As principais síndromes autoinflamatórias são causadas por defeitos monogênicos em proteínas da imunidade inata, sendo consideradas imunodeficiências primárias. Elas são caracterizadas clinicamente por sintomas inflamatórios sistêmicos recorrentes ou contínuos e devem ser diferenciadas das doenças infecciosas, autoimunes e outras imunodeficiências primárias. Nesta revisão, foram enfatizadas características epidemiológicas, manifestações clínicas, alterações laboratoriais, prognóstico e terapia das principais síndromes autoinflamatórias: febre familiar do Mediterrâneo; síndrome periódica associada ao receptor de fator de necrose tumoral; criopirinopatias; deficiência de mevalonato-quinase; artrite granulomatosa pediátrica; síndrome de pioderma gangrenoso, artrite piogênica e acne; síndrome de Majeed; e deficiência do antagonista do receptor de interleucina-1. As criopirinopatias discutidas foram: doença inflamatória multissistêmica de início neonatal ou síndrome neurológica, cutânea e articular crônica infantil, síndrome de Muckle-Wells e síndrome autoinflamatória familiar associada ao frio. CONCLUSÕES: É importante que o pediatra reconheça as síndromes autoinflamatórias hereditárias mais prevalentes, pois o encaminhamento ao reumatologista pediátrico pode permitir um diagnóstico precoce e uma instituição de tratamento adequado, possibilitando uma melhora da qualidade de vida dos pacientes.

OBJECTIVE: To describe the most prevalent pediatric hereditary autoinflammatory syndromes. SOURCES: A review of the literature including relevant references from the PubMed and SciELO was carried out using the keywords autoinflammatory syndromes and child. SUMMARY OF THE FINDINGS: The hereditary autoinflammatory syndromes are caused by monogenic defects of innate immunity and are classified as primary immunodeficiencies. These syndromes are characterized by recurrent or persistent systemic inflammatory symptoms and must be distinguished from infectious diseases, autoimmune diseases, and other primary immunodeficiencies. This review describes the epidemiological, clinical and laboratory features, prognosis, and treatment of the main autoinflammatory syndromes, namely: familial Mediterranean fever; TNF receptor associated periodic syndrome; the cryopyrinopathies; mevalonate kinase deficiency; pediatric granulomatous arthritis; pyogenic arthritis, pyoderma gangrenosum and acne syndrome; Majeed syndrome; and deficiency of interleukin 1 receptor antagonist. The cryopyrinopathies discussed include neonatal-onset multisystem inflammatory disease (also known as chronic infantile neurologic, cutaneous and articular syndrome) Muckle-Wells syndrome, and familial cold autoinflammatory syndrome. CONCLUSIONS: Pediatricians must recognize the clinical features of the most prevalent autoinflammatory syndromes. Early referral to a pediatric rheumatologist may allow early diagnosis and institution of treatment, with improvement in the quality of life of these patients.