Genetic testing in autoinflammatory diseases - past, current and future perspectives

Genetically Transitional Disease and the Road to Personalized Medicine

Genetically transitional disease (GTD) is emerging as a new concept in genomic medicine to straddle between the traditional binary classification of monogenic and polygenic disease. Genetic testing result reports in molecular laboratories have been predicated on the monogenic disease model, which focuses on pathogenic and likely pathogenic variants. While variants of uncertain significance (VUS) are reported by laboratories, there are challenges with regard to their clinical application so that these variants are often dismissed by ordering physicians. Unlike Mendelian disorders, where genetic variants are of high penetrance and highly probabilistic, the GTD concept is employed to highlight the impact of low-to-moderate effect gene variants whose influence on disease is modified by the genetic background. The GTD concept may explain health conditions associated with variants that are necessary but not sufficient for pathogenesis, lying in the mid gray zone between Mendelian and polygenic diseases. Although VUSs may not reach the level of pathogenicity based on American College of Medical Genetics and Genomics guidelines, they could be provisionally classified as GTD-associated variants to annotate and interpret the relationship between VUS and human genetic disease. The appropriate implementation of the GTD concept could impact patient care and research by focusing attention on the individual variability of responses in various diseases.

Molecular genetics in adult-onset Still's disease: next-generation sequencing in 24 patients and literature review

Objective

Next-generation sequencing (NGS) panels are increasingly used for the diagnosis of monogenic systemic autoinflammatory diseases (SAIDs). However, their role in patients with adult-onset Still's disease (AOSD) remains unknown. This study aims to assess the usefulness of NGS panels in AOSD patients to improve diagnosis and management of the disease.

Methods

This observational, multicenter study included all patients with AOSD diagnosis who underwent NGS panel testing in northern Spain. Clinical manifestations, laboratory parameters, complications, and therapeutic responses were recorded.

Results

A total of 24 patients (16 men, 8 women) with an average age of 42.2 ± 17.9 (mean ± SD) years, in whom NGS was performed, fulfilled the Yamaguchi and/or Fautrel criteria for AOSD. The most common symptoms, apart from fever, were skin rash (75%), asthenia (91.7%), and articular manifestations (91.7%). All patients had elevated acute-phase reactant levels and hyperferritinemia. Almost all patients received oral glucocorticoids as initial therapy. Conventional disease-modifying antirheumatic drugs (cDMARDs) were used in 17 (70.8%) patients and biologic therapy in 13 (54.1%) patients. Genetic variants were observed in 5 (20.8%) patients. None of them were classified as pathogenic. Variants of uncertain significance (VUS) were identified in NOD2 (c.2104C>T and c.2251G>A), TNFRSF1A (c.224C>T), TNFAIP3 (c.1939A>C), and SCN9A (c.2617G>A). Atypical manifestations and/or therapeutic refractoriness were observed in patients carrying genetic variants, except for one patient with the TNFAIP3 VUS. Four out of five patients with VUS had a severe and refractory course of the disease and required biologic therapy.

Conclusion

NGS was useful to rule out the presence of pathogenic genetic variants related to other SAIDs and to detect VUS that may help identify patients at risk for atypical and severe manifestations and poor response to conventional therapy.

Genetic Approaches to Study Rheumatic Diseases and Its Implications in Clinical Practice

Patients with rare and complex rheumatic diseases (RDs) present with immense clinical variability inherent to all immunologic diseases. In addition to systemic and organ-specific inflammation, patients may display features of immunodeficiency or allergy, which may represent major diagnostic and therapeutic challenges. The person's genetic architecture has been a well-established risk factor for patients with RDs, albeit to variable degrees. Patients with early-onset diseases and/or positive family history (FH) have a strong genetic component, whereas patients with late-onset RDs demonstrate a more complex interplay of genetic and environmental risk factors. Overall, the genetic studies in patients with RDs have been instrumental to our understanding of innate and adaptive immunity in human health and disease. The elucidation of the molecular causes underlying rare diseases has played a major role in the identification of genes that are critical in the regulation of inflammatory responses. In addition, studies of patients with rare disorders may help determine the mechanisms of more complex autoimmune diseases by identifying variants with small effect sizes in the same genes. In contrast, studies of patients with common RDs are conducted in cohorts of patients with well-established phenotypes and ancestry-matched controls, and they aim to discover disease-related pathways that can inform the development of novel targeted therapies. Knowing the genetic cause of a disease has helped patients and families understand the disease progression and outcome. Here, we discuss the current understanding of genetic heritability and challenges in the diagnosis of RDs in patients and how this field may develop in the future.

Genetic and clinical features of familial mediterranean fever (FMF) in a homogeneous cohort of patients from South-Eastern Italy

Familial Mediterranean Fever (FMF) is linked with the MEFV gene and is the commonest among monogenic autoinflammatory diseases, with high prevalence in the Mediterranean basin. Although the clinical presentation of FMF has a major role in diagnosis, genotype/phenotype correlations and the role of "benign" gene variants (as R202Q) appear highly variable and incompletely clear, making difficult to select the most effective strategy in the management of patients. Aim of the present study was to investigate the clinical presentation and the genetic background in a homogenous cohort of patients from Apulia (south eastern Italy). We investigated 217 patients with a clinical suspect of autoinflammatory diseases, who were characterized for the occurrence of specific symptoms and with next generation sequencing by a 4-gene panel including MEFV, MVK, NLRP3 and TNFRSF1A. A genetic change was identified in 122 (53.7%) patients, with 161 different MEFV variants recorded in 100 individuals, 10 variants in NLRP3, and 6 each in TNFRSF1A and MVK. The benign variant R202Q was largely prevalent (41.6% of all MEFV variants). When patients were selected according the number of pathogenic MEFV variants (0, 1, or 2 pathogenic variants), results failed to show significant links between the frequency of symptoms and the number of pathogenic variants. Only family history and Pras score (indicative for severity of disease) predicted the presence of pathogenic variants, as compared with carriers of variants considered of uncertain significance or benign. Fever >38 °C and arthralgias appeared more frequently in R202Q-positive patients than in non-R202Q carriers. These two subgroups showed comparable duration of fever, occurrence of myalgia, abdominal and chest pain, Pras, and IFFS scores. In conclusion, results confirm that FMF manifests in mild form in non-middle eastern patients. This possibility partly affects the reliability of clinical criteria/scores. Furthermore, the presence of the R202Q variant might not be completely neutral in selected groups of patients.