Typical myelodysplastic syndrome (MDS) associated with isolated del(5q) consists of an interstitial deletion of the band between q13 and q33 on chromosome 5. Generally, patients with isolated deletion 5q have better outcomes than those who have the deletion 5q with additional karyotypic abnormalities. Here we report a 47 year-old female with an isolated del(5q) chromosomal abnormality with an atypical breakpoint of 5q11q35 and rapid progression to acute leukemia, which had an exceptionally poor outcome. The peripheral blood revealed pancytopenia and occasional giant platelets, and the patient had hypercellular bone marrow with 4.8% blasts, as well as dysmegakaryopoiesis and dyserythropoiesis. Cytogenetically, the patient was del(5q)(q11.2q35)[18]/46,XX[2], showing that her deleted region was larger than that found for typical del 5q syndrome. Three months later, the patient presented with acute myelomonocytic leukemia with multilineage dysplasia. The cytogenetic findings were identical. Two months after allogeneic bone marrow transplantation, the patient died from severe graft-versus host disease.

Keywords: Myelodysplastic syndromes, Isolated deletion(5q)