[Protein S deficiency in three patients with thrombosis]

Protein S (PS) deficiency, which is caused by various factors including congenital and acquired disorders, is a risk factor for thrombophilia. We described 3 patients with different backgrounds, who all exhibited PS deficiency. The first patient was a 47-year-old woman who suffered from frequent cerebral infarctions, deep-vein thrombosis (DVT) of her lower extremities, and pulmonary thromboembolism. Her son suffered from skin necrosis due to PS deficiency and both had the same mutant allele of the PS gene. The second patient was a 50-year-old woman who experienced a cold sensation in her fingers. Her relatives had a history of cerebrovascular disease. No mutation was detected in her PS gene. The third patient was a 27-year-old man with antiphospholipid antibody. He suffered from thrombocytopenia, skin necrosis, DVT of his lower extremities, and pulmonary thromboembolism. A mutation was identified in the steroid hormone-binding globulin-like (SHBG) domain of his PS gene. Neither his parents nor siblings had a history of thrombosis. The mutations found in the first and third patients were both missense mutations in the SHBG domain that have not been reported previously. The third patient had a mutation in the site that is involved in binding to C4b-binding protein, which modifies the immune response. These three cases provide key insights into the pathophysiology of PS deficiency.