Persistent thrombocytosis in elderly patients with rare hyposplenias that mimic essential thrombocythemia.

When elderly patients present with persistent thrombocytosis, myeloproliferative disease, iron-deficiency anemia or post-splenectomy status are suspected along with autoimmune diseases. Reported here are the cases of two elderly patients with persistent thrombocytosis due to hyposplenia, which is very rarely diagnosed in old age. Case 1 was a 72-year-old man whose thrombocytosis was due to non-familial type isolated congenital asplenia. Case 2 was a 74-year-old man whose thrombocytosis was caused by an atrophied spleen resulting from perforated stomach ulcer-related panperitonitis that had been treated 20 years previously. Both patients had thrombocyte counts exceeding >500,000/μl in association with small vestigial spleen tissue on a computed tomography scan and positive Howell-Jolly bodies on the blood smear. A correct diagnosis is essential for the management of persistent thrombocytosis.