Chromosome 5q deletion syndrome

Chromosome 5q deletion syndrome (chromosome 5q monosomy, 5q- syndrome) is a rare disorder caused by loss of part of the long arm (q arm, band 5q31.1) of human chromosome 5.

It should not be confused with "partial trisomy 5q", though both conditions have been observed in the same family.

This should not be confused with cri du chat syndrome which is a deletion of the short arm of the 5th chromosome.

Characteristics
The 5q-syndrome is characterized by macrocytic anemia often thrombocytosis, erythroblastopenia, megakaryocyte hyperplasia with nuclear hypolobation and an isolated interstitial deletion of chromosome 5. The 5q- syndrome is found predominantly in females of advanced age.

Causes
An association with RPS14 has been identified.

Deletion of the miR-145 and miR-146 loci has been associated with elevated platelet count and megakaryocytic dysplasia associated with the 5q- syndrome.

Histology
This syndrome affects bone marrow cells causing treatment-resistant anemia and myelodysplastic syndromes that may lead to acute myelogenous leukemia. Examination of the bone marrow shows characteristic changes in the megakaryocytes. They are more numerous than usual, small and mononuclear. There may be accompanying erythroid hypoplasia in the bone marrow.

Treatment
Lenalidomide is a new agent that is showing promise in treating 5q- syndrome. It is approved for a subset of cases.

Prognosis
Most patients have a stable clinical course but are often transfusion dependent.