TNF inhibitors are currently amongst the highest grossing drugs on the market, and have radically improved treatment of autoimmune diseases including rheumatoid arthritis and the skin disease psoriasis. TNF appears to play conflicting role in cancer, having historically been viewed as having anti-tumour activity, but recently being increasingly characterised as a pro-carcinogenic constituent of the tumour microenvironment. Furthering our understanding of TNF signalling has important implications for both cancer and inflammatory diseases, disease states which can become intertwined in the setting of the promotion of carcinogenesis by chronic inflammation. The inactivating chronic proliferative dermatitis mutation (cpdm) in the Sharpin gene causes dermatitis in mice with epidermal hyperplasia and lesions by 5-8 weeks of age that resemble human psoriasis. Our group and collaborators1 have shown that SHARPIN forms part of a linear ubiquitin chain assembly complex (LUBAC) at tumour necrosis factor (TNF) receptor 1. LUBAC linear ubiquitylation is essential for full strength NF-kB signalling and prevention of TNF induced cell death. Here we show that TNF deficiency completely rescues Sharpincpdm/cpdm dermatitis. In-vivo clodrosome depletion of macrophages, potent sources of TNF, was also protective. In epidermal keratinocytes, TNF induced both apoptotic and necroptotic cell death, the latter being a form of programmed necrosis dependent on RIP3. Because necroptosis is more inflammatory than apoptosis, we hypothesized that Sharpincpdm/cpdm dermatitis is caused by necroptotic cells leaking cellular contents and driving inflammation. However, RIP3 deficiency only partly and variably rescued the disease. Although dogma is that apoptosis is generally immunologically silent, these data raise the possibility that excessive apoptosis may also be pathogenic.