Protein S deficiency

Protein S deficiency is a disorder that increases the risk of developing blood clots. People with protein S deficiency are at risk of developing a type of clot called a deep vein thrombosis (DVT) that occurs in the deep veins of the arms or legs. A DVT can travel through the bloodstream and lodge in the lungs, causing a life-threatening clot called a pulmonary embolism (PE). Both DVTs and PEs are a type of venous thromboembolism, a general term for blood clots that form in a vein. Factors such as age, surgery, immobility, or pregnancy can increase the risk of clotting in people with protein S deficiency. In addition, people who have protein S deficiency and another inherited blood clotting disorder may have a higher risk of developing blood clots. Venous thromboembolism occurs in approximately fifty to sixty percent of people with protein S deficiency. 

In rare cases, individuals have a severe form of protein S deficiency with signs and symptoms that develop soon after birth. Affected infants typically develop a life-threatening blood clotting disorder called purpura fulminans. Purpura fulminans is characterized by the formation of blood clots within small blood vessels throughout the body. These blood clots disrupt normal blood flow and can lead to the death of tissues (necrosis). Widespread blood clotting uses up all available blood clotting proteins. As a result, the body can no longer create clots, and bleeding occurs in various parts of the body. This abnormal bleeding often appears as large, purple skin lesions. Affected individuals who survive the newborn period may experience recurrent episodes of purpura fulminans.