Zimmermann N, et al. - Researchers assessed the clinical response to the Janus kinase inhibitor baricitinib in familial chilblain lupus, a monogenic autosomal dominant form of cutaneous lupus erythematosus that, in most cases, is caused by mutations in the 3 prime repair exonuclease 1 (TREX1), and evaluated the impact of cold on patient fibroblasts. For this case series, 3 patients (2 women and 1 man) with familial chilblain lupus due to TREX1 mutation had treatment with baricitinib for 3 months. The findings showed the therapeutic effectiveness of Janus kinase inhibition in a monogenic lupus form in three patients and provided mechanistic insight into the cold exacerbation process in TREX1-deficient cells. For multifactorial cutaneous lupus erythematosus, this finding might be relevant to other type I interferon (IFN)–mediated disorders and suggests Janus kinase inhibition as a potential therapeutic option also. There were no reported severe adverse reactions.