Myelodysplastic syndrome with isolated 5q deletion (5q- syndrome). A clonal stem cell disorder characterized by defective ribosome biogenesis.

Perspective article on myelodysplastic syndrome with deltion 5q. In 1974 Herman van den Berghe et al. reported a distinct hematologic disorder associated with acquired deletion of the long arm of chromosome 5 [del(5q)]. This novel nosological entity was described in more detail one year later by Sokal, van den Berghe, and coworkers. Patients with del(5q) had macrocytic anemia with oval macrocytes, normal to slightly reduced white blood cell counts, and normal to elevated platelet counts. With respect to the bone marrow, there was erythroid hypoplasia but "the most striking abnormality concerned the megakaryocytes and especially their nuclei, which were generally small, round or oval, and nonlobulated". Until that time, the only specific chromosomal abnormality in hematologic disorders was the Philadelphia chromosome associated with chronic myeloid leukemia. Sokal et al. concluded that del(5q) represented a novel specific chromosomal abnormality associated with refractory anemia, although they had no explanation to connect the abnormal chromosome 5 with the hematologic manifestations.