Case Report: Severe protein S deficiency unmasks a cryptic PROC mutation with normal activity, triggering life-threatening pulmonary thromboembolism

Background: defect may remain latent until unmasked by a profound cofactor deficiency, such as severe PS deficiency. This synergistic mechanism, and the catastrophic thrombosis it may precipitate, has not been previously documented. Case presentation: (c.577_579delAAG, p.Lys193del), inherited from his asymptomatic parents respectively. Conclusions: , in young patients with high-risk PTE even when PC activity is normal.