Menezes, JulianeVentura, CéliaMatos Costa, JoãoParreira, ElsaRomão, LuísaGonçalves, João2018-03-012018-03-012017-11-03Clin Case Rep. 2017 Nov 3;5(12):2062-2065. doi: 10.1002/ccr3.1226. eCollection 2017 Dec2050-0904http://hdl.handle.net/10400.18/5109Protein S (PS) is a widely studied protein with an important function in the downregulation of thrombin formation. Since its discovery in 1976, more than 400 variants have been described in PS gene (PROS1) associated with PS deficiency and as a risk factor for venous thromboembolism (VTE). We describe a novel variant, c.1871-14T>G, in intron 14 of PROS1 gene identified in two patients with PS deficiency from two unrelated families with a history of thrombotic disease. This alteration leads to a PROS1 mRNA expression reduction, probably due to nonsense-mediated mRNA decay. Our results suggest that c.1871-14T>G is causative of type I PS deficiency in these patients, highlighting the importance of screening not only the coding and the most conserved intron–exon junctions, but also perform mRNA-based studies. We call attention to the potential increased risk of VTE in hereditary type I PS deficiency associated with this cryptic splice-site variant.Key Clinical Message: Our results prove that c.1871-14T>G is causative of type I PS deficiency, highlighting the importance of performing mRNA-based studies in order to evaluate variants pathogenicity. We evidence the increased risk of venous thromboembolism associated with this cryptic splice-site variant if present in patients with PS deficiency.engPROS1Protein S DeficiencyThrombophiliaThrombosisVenous Thromboembolism.SplicingSplice-siteDoenças Genéticasjournal article10.1002/ccr3.1226