 <unk> conditions associated with sluggish blood flow can increase risk for thrombosis . For example , sickle @-@ cell disease ( caused by mutations of hemoglobin ) is regarded as a mild prothrombotic state induced by impaired flow . Similarly , myeloproliferative disorders , in which the bone marrow produces too many blood cells , predispose to thrombosis , particularly in polycythemia vera ( excess red blood cells ) and essential <unk> ( excess platelets ) . Again , these conditions usually warrant specific treatment when identified . 
