RESUMO
Deep venous thrombosis is a rare disease in children under the age of 18, with an estimated incidence of 1/100,000 per year in Hungary. Its typical localization in children is in the extremities, usually occurring in newborns and in teenagers. Both congenital and acquired risk factors can be in the background. Although it is a rarity, we should think of it, because late diagnosis can cause life-threatening conditions like pulmonary embolism or central nervous system thrombosis. Detailed medical history can help the diagnosis. Etiology, possible congenital and acquired risk factors, as well as diagnostic and therapeutic options are discussed through three cases of teenage children. Diagnostic difficulties of deep venous thrombosis in childhood are the following: the occurrence is rarer than in adulthood therefore it is often forgotten as a possible diagnosis, coagulation parameters are age-dependent, and diagnosis with imaging techniques is more difficult.