Systemic autoinflammatory diseases are driven by abnormal activation of innate immunity1. Herein we describe a new syndrome caused by high penetrance heterozygous germline mutations in the NFκB regulatory protein TNFAIP3 (A20) in six unrelated families with early onset systemic inflammation. The syndrome resembles Behçet’s disease (BD), which is typically considered a polygenic disorder with onset in early adulthood2. A20 is a potent inhibitor of the NFκB signaling pathway3. TNFAIP3 mutant truncated proteins are likely to act by haploinsufficiency since they do not exert a dominant-negative effect in overexpression experiments. Patients’ cells show increased degradation of IκBα and nuclear translocation of NFκB p65, and increased expression of NFκB-mediated proinflammatory cytokines. A20 restricts NFκB signals via deubiquitinating (DUB) activity. In cells expressing the mutant A20 protein, there is defective removal of K63-linked ubiquitin from TRAF6, NEMO, and RIP1 after TNF stimulation. NFκB-dependent pro-inflammatory cytokines are potential therapeutic targets for these patients.

Systemic autoinflammatory diseases are caused by mutations in genes that function in innate immunity. Here, we report an autoinflammatory disease caused by loss-of-function mutations in OTULIN (FAM105B), encoding a deubiquitinase with linear linkage specificity. We identified two missense and one frameshift mutations in one Pakistani and two Turkish families with four affected patients. Patients presented with neonatal-onset fever, neutrophilic dermatitis/panniculitis, and failure to thrive, but without obvious primary immunodeficiency. HEK293 cells transfected with mutated OTULIN had decreased enzyme activity relative to cells transfected with WT OTULIN, and showed a substantial defect in the linear deubiquitination of target molecules. Stimulated patients' fibroblasts and peripheral blood mononuclear cells showed evidence for increased signaling in the canonical NF-κB pathway and accumulated linear ubiquitin aggregates. Levels of proinflammatory cytokines were significantly increased in the supernatants of stimulated primary cells and serum samples. This discovery adds to the emerging spectrum of human diseases caused by defects in the ubiquitin pathway and suggests a role for targeted cytokine therapies.OTULIN | linear deubiquitinase | NF-κB pathway | autoinflammatory disease | cytokines

Receptor Interacting Protein Kinase 1 (RIPK1) is a key regulator of innate immune signalling pathways. To ensure an optimal inflammatory response, RIPK1 is post-translationally regulated by well characterised ubiquitylation and phosphorylation events, as well as caspase-8 mediated cleavage 1-7. The physiological relevance of this cleavage remains unclear, though it is believed to inhibit activation of RIPK3 and necroptosis 8. Here we show that heterozygous missense mutations p.D324N, p.D324H and p.D324Y prevent caspase cleavage of RIPK1 in humans and result in early-onset periodic fever episodes and severe intermittent lymphadenopathy, a condition we designate 'Cleavage-resistant RIPK1-Induced Autoinflammatory' (CRIA) syndrome. To define the mechanism for this disease we generated a cleavage-resistant Ripk1 D325A mutant mouse strain. While Ripk1-/mice die postnatally from systemic inflammation, Ripk1 D325A/D325A mice died during embryogenesis. Embryonic lethality was completely prevented by combined loss of Casp8 and Ripk3 but not by loss of Ripk3 or Mlkl alone. Loss of RIPK1 kinase activity also prevented Ripk1 D325A/D325A embryonic lethality, however the mice died before weaning from multi organ inflammation in a RIPK3 dependent manner. Consistently, Ripk1 D325A/D325A and Ripk1 D325A/+ cells were hypersensitive to RIPK3 dependent TNF-induced apoptosis and necroptosis. Heterozygous Ripk1 D325A/+ mice were viable and grossly normal, but were hyper-responsive to inflammatory stimuli in vivo. Our results demonstrate the importance of caspase-mediated RIPK1 cleavage during embryonic development and show that caspase cleavage of RIPK1 not only inhibits necroptosis but maintains inflammatory homeostasis throughout life. Members of three families presented with a previously undescribed autoinflammatory disorder characterised by fevers and pronounced lymphadenopathy beginning in early childhood and continuing throughout adulthood (Fig. 1a). From birth or shortly thereafter, all affected individuals experienced fevers usually occurring approximately every 2-4 weeks, Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Genetic studies identified