The syndrome is found predominantly in women older than 50 years of age.
Features:
(1) cytogenetic abnormalities limited to 5q- (affecting the long arm of chromosome 5)
(2) refractory anemia with macrocytic indices
(3) vitamin B12 or folate deficiency excluded
(4) moderate leukopenia
(5) normal to elevated platelet count, with hypolobated megakaryocytes
Exclusions requiring classification as another form of myelodysplastic syndrome:
(1) any other cytogenetic abnormalities
(2) >= 5% blasts in the bone marrow or peripheral blood
(3) >= 15% ringed sideroblasts
(4) significant multilineage dysplasia (see refractory cytopenia with multilineage dysplasia)
(5) monocytosis > 1,000 per µL
The prognosis of the syndrome as strictly defined is favorable with a low rate of progression to acute leukemia. The appearance of additional cytogenetic abnormalities correlates with disease progression.
