Isolated spleen agenesis: a rare cause of thrombocytosis mimicking essential thrombocythemia

Thrombocytosis is a common feature of myeloproliferative disorders but may also result from various conditions including chronic iron deficiency, hemo rrhage, chronic inflammation and splenectomy. We report two cases of second ary thrombocytosis caused by isolated and congenital asplenia, mimicking es sential thrombocythemia. These two adult cases of spleen agenesis were unex pected. We conclude that in thrombocytosis without clinical evidence of spl enomegaly, attentive screening of blood in search of Howell-Jolly bodies an d abdominal ultrasonography should always be performed not only to detect m ild spleen enlargement but also to make pressure of the presence of this or gan. (C)2000; Ferrata Storti Foundation.