Daniela Ionescu1, Alejandro Peñín-Franch2, Anna Mensa-Vilaró3, Paola Castillo4, Laura Hurtado-Navarro2, Cristina Molina-López2, Silvia Romero-Chala1, Susana Plaza3, Virginia Fabregat3, Segundo Buján5, Joana Marques5, Ferran Casals6, Jordi Yagüe4, Baldomero Oliva7, Luis Miguel Fernández-Pereira1, Pablo Pelegrín8, Juan I Aróstegui4. 1. Hospital San Pedro de Alcántara, Cáceres, Spain. 2. Instituto Murciano de Investigación Biosanitaria IMIB-Arrixaca and Hospital Clínico Universitario Virgen de la Arrixaca, El Palmar, Murcia, Spain. 3. Hospital Clínic de Barcelona, Barcelona, Spain. 4. Hospital Clínic de Barcelona, Institut d'Investigacions Biomèdiques August Pi i Sunyer, and Universitat de Barcelona, Barcelona, Spain. 5. Hospital Universitari Vall d'Hebron, Barcelona, Spain. 6. Universitat Pompeu Fabra and Parc de Recerca Biomèdica de Barcelona, Barcelona, Spain. 7. Structural Bioinformatics Lab GRIB-IMIM, Universitat Pompeu Fabra, and Parc de Recerca Biomèdica de Barcelona, Barcelona, Spain. 8. Instituto Murciano de Investigación Biosanitaria IMIB-Arrixaca and Hospital Clínico Universitario Virgen de la Arrixaca, El Palmar, and University of Murcia, Murcia, Spain.
Abstract
OBJECTIVE: Autoinflammatory diseases are inherited disorders of innate immunity that usually start during childhood. However, several recent reports have described an increasing number of patients with autoinflammatory disease starting in adulthood. This study was undertaken to investigate the underlying cause of a case of late-onset uncharacterized autoinflammatory disease. METHODS: Genetics studies were performed using Sanger sequencing and next-generation sequencing (NGS) methods. In silico, in vitro, and ex vivo analyses were performed to determine the functional consequences of the detected variant. RESULTS: We studied a 57-year-old woman who at the age of 47 years began to have recurrent episodes of fever, myalgias, arthralgias, diffuse abdominal pain, diarrhea, adenopathies, and systemic inflammation, which were relatively well controlled with anti-interleukin-1 (anti-IL-1) drugs. NGS analyses did not detect germline variants in any of the known autoinflammatory disease-associated genes, but they identified the p.Ser171Phe NLRC4 variant in unfractionated blood, with an allele fraction (2-4%) compatible with gene mosaicism. Structural modeling analyses suggested that this missense variant might favor the open, active conformation of the NLRC4 protein, and in vitro and ex vivo analyses confirmed its propensity to oligomerize and activate the NLRC4 inflammasome, with subsequent overproduction of IL-18. CONCLUSION: Our findings indicate that the postzygotic p.Ser171Phe NLRC4 variant is a plausible cause of the disease in the enrolled patient. Functional and structural studies clearly support, for the first time, its gain-of-function behavior, consistent with previously reported NLRC4 pathogenic variants. These novel findings should be considered in the diagnostic evaluation of patients with adult-onset uncharacterized autoinflammatory disease.
OBJECTIVE: Autoinflammatory diseases are inherited disorders of innate immunity that usually start during childhood. However, several recent reports have described an increasing number of patients with autoinflammatory disease starting in adulthood. This study was undertaken to investigate the underlying cause of a case of late-onset uncharacterized autoinflammatory disease. METHODS: Genetics studies were performed using Sanger sequencing and next-generation sequencing (NGS) methods. In silico, in vitro, and ex vivo analyses were performed to determine the functional consequences of the detected variant. RESULTS: We studied a 57-year-old woman who at the age of 47 years began to have recurrent episodes of fever, myalgias, arthralgias, diffuse abdominal pain, diarrhea, adenopathies, and systemic inflammation, which were relatively well controlled with anti-interleukin-1 (anti-IL-1) drugs. NGS analyses did not detect germline variants in any of the known autoinflammatory disease-associated genes, but they identified the p.Ser171Phe NLRC4 variant in unfractionated blood, with an allele fraction (2-4%) compatible with gene mosaicism. Structural modeling analyses suggested that this missense variant might favor the open, active conformation of the NLRC4 protein, and in vitro and ex vivo analyses confirmed its propensity to oligomerize and activate the NLRC4 inflammasome, with subsequent overproduction of IL-18. CONCLUSION: Our findings indicate that the postzygotic p.Ser171Phe NLRC4 variant is a plausible cause of the disease in the enrolled patient. Functional and structural studies clearly support, for the first time, its gain-of-function behavior, consistent with previously reported NLRC4 pathogenic variants. These novel findings should be considered in the diagnostic evaluation of patients with adult-onset uncharacterized autoinflammatory disease.