Ringed sideroblasts with thrombocytosis: an uncommon mixed myelodysplastic/myeloproliferative disease of older adults.

Sideroblastic anaemia with ringed sideroblasts and marked thrombocytosis, hereupon referred to as ringed sideroblasts with thrombocytosis (RST), is a provisional entity in the 2001 World Health Organisation classification scheme. This retrospective study identified 16 patients with RST over a 7-year period. Proposed diagnostic criteria include a sustained platelet count > 500 x 10(9)/l, > or = 15% ringed sideroblasts, < 3% bone marrow blasts, and normal conventional cytogenetics. The median age was 76 years with eight males and eight females. With a median follow-up of 41 months, RST patients had a median overall survival of 71 months, comparable with refractory anaemia having ringed sideroblasts, but less favourable than essential thrombocythaemia. Thus far, no patients with RST are known to have died of disease-related causes. Patients with ringed sideroblasts and/or thrombocytosis need to be carefully evaluated for a variety of haematological diseases that may confer significantly different prognoses.