Gain-of-function mutations in<i>ALPK1</i>cause an NF-κB-mediated autoinflammatory disease: functional assessment, clinical phenotyping and disease course of patients with ROSAH syndrome

<jats:sec><jats:title>Objectives</jats:title><jats:p>To test the hypothesis that ROSAH (retinal dystrophy, optic nerve oedema, splenomegaly, anhidrosis and headache) syndrome, caused by dominant mutation in<jats:italic>ALPK1</jats:italic>, is an autoinflammatory disease.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>This cohort study systematically evaluated 27 patients with ROSAH syndrome for inflammatory features and investigated the effect of<jats:italic>ALPK1</jats:italic>mutations on immune signalling. Clinical, immunologic and radiographical examinations were performed, and 10 patients were empirically initiated on anticytokine therapy and monitored. Exome sequencing was used to identify a new pathogenic variant. Cytokine profiling, transcriptomics, immunoblotting and knock-in mice were used to assess the impact of<jats:italic>ALPK1</jats:italic>mutations on protein function and immune signalling.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The majority of the cohort carried the p.Thr237Met mutation but we also identified a new ROSAH-associated mutation, p.Tyr254Cys.</jats:p><jats:p>Nearly all patients exhibited at least one feature consistent with inflammation including recurrent fever, headaches with meningeal enhancement and premature basal ganglia/brainstem mineralisation on MRI, deforming arthritis and AA amyloidosis. However, there was significant phenotypic variation, even within families and some adults lacked functional visual deficits. While anti-TNF and anti-IL-1 therapies suppressed systemic inflammation and improved quality of life, anti-IL-6 (tocilizumab) was the only anticytokine therapy that improved intraocular inflammation (two of two patients).</jats:p><jats:p>Patients’ primary samples and in vitro assays with mutated ALPK1 constructs showed immune activation with increased NF-κB signalling, STAT1 phosphorylation and interferon gene expression signature. Knock-in mice with the<jats:italic>Alpk1</jats:italic>T237M mutation exhibited subclinical inflammation.</jats:p><jats:p>Clinical features not conventionally attributed to inflammation were also common in the cohort and included short dental roots, enamel defects and decreased salivary flow.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>ROSAH syndrome is an autoinflammatory disease caused by gain-of-function mutations in<jats:italic>ALPK1</jats:italic>and some features of disease are amenable to immunomodulatory therapy.</jats:p></jats:sec>