Monogenic interferon-mediated diseases: novel phenotype and genotype characteristics from a Saudi population.

Objectives: IFN-mediated diseases are mendelian innate immunodysregulatory disorders that present early in life with fevers, sterile organ inflammation, and a high type-I IFN-response gene signature in peripheral blood cells. To date, monumental discoveries of novel genetic variants with various phenotypic features have been recognised. We aimed to describe the genotype and phenotype findings in Saudi children diagnosed with autoinflammatory interferonopathy and to report novel findings.

Methods: This is a descriptive retrospective cohort study of children with genetically confirmed type I interferonopathies. Medical records were reviewed for demographic, family history, clinical and laboratory data. All patients underwent genetic testing.

Results: A total of 20 patients (11 females) were included in the study. Sixteen patients (80%) presented within the first 2 years. The median age of disease onset was 0.87 years (IQR: 0.5-2) and the median age of diagnosis was 4.5 years (IQR: 2-7.5). The rates of consanguinity and family history of affected members were high (88% and 47%, respectively). Among the cohort of patients, whole exome sequencing was conducted for 15 patients. Three patients underwent targeted gene tests, and 2 patients had a leukoencephalopathy genetic panel. Eight patients were diagnosed with Aicardi-Goutières syndrome, attributed to variants in the RNASEH2A, RNASEH2C, and IFIH1 genes. Additionally, 2 patients were identified with STING-associated vasculopathy with onset in infancy linked to the TMEM173 variant. One patient exhibited chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature due to PSMB8, and another patient had DNase II. Moreover, 8 patients presented with rare interferonopathy conditions, including three with ISG15, 3 with ZNFX1, 1 with the SOCS1 variant, and 1 the STAT1 variant. Of 12 variants, six (50%) found to have novel genetic variants. The most frequent features were fever (75%), neurology (70%), mucocutaneous (60%), gastrointestinal (50%), and pulmonary (50%). Hypogammaglobinaemia and recurrent infections were seen in (45%) and (20%), respectively. Fifteen patients (75%) had elevated inflammatory markers. The majority of patients received intensive treatment, including corticosteroids, JAK inhibitors, IVIG, and various immunosuppressive agents. Despite these interventions, a partial response to treatment was observed, and cumulative disease damage primarily manifested as growth failure and developmental delay.

Conclusions: Our findings support the previous reports; early-onset fever, neurology, and respiratory features should raise the suspicion of interferonopathies. However, there is eminent evidence of phenotypic variability. Our data also expanded the spectrum of clinical findings in relation to novel genetic variants.