# del(5q) (5q- syndrome and lenalidomide response)

Source: https://onco.cc/terms/del5q/  
OnCo record `del5q` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Losing a piece of the long arm of chromosome 5 causes a distinctive low-risk myelodysplastic syndrome, typically an older woman with severe anaemia and a normal or high platelet count; it is the one MDS with a drug matched to its genetics, lenalidomide, which makes two-thirds of patients transfusion-free unless TP53 is also mutated.

## Summary

What is measured: an interstitial deletion of the long arm of chromosome 5. How: marrow karyotype (G-banding) and FISH with 5q31 or 5q33 probes (EGR1, CSF1R) at diagnosis and in follow-up; WHO 2022 defines MDS with low blasts and isolated 5q deletion, allowing one additional abnormality other than monosomy 7 or del(7q); the marrow shows hypolobated megakaryocytes; TP53 is sequenced because a subclonal mutation, present in about a fifth at diagnosis, predicts lenalidomide failure and progression; the deletion counts as a good-risk cytogenetic category in IPSS-R. Mechanism: haploinsufficiency of RPS14 (anaemia), CSNK1A1 (lenalidomide degrades casein kinase 1 alpha through cereblon and so kills the clone selectively) and the miR-145/146a locus (thrombocytosis). What a result changes: transfusion-dependent anaemia in lower-risk del(5q) MDS is treated with lenalidomide 10 mg (MDS-003 and MDS-004: transfusion independence in 56 to 67 percent, with cytogenetic responses), dose-adjusted for the neutropenia and thrombocytopenia it causes; a TP53 mutation weakens the response and pushes towards hypomethylating agents or transplant; in other lower-risk MDS the drug helps only about a quarter; progression to AML (10 to 20 percent) is watched for. Where it matters: lower-risk MDS, and higher-risk MDS when del(5q) sits within a complex karyotype.

## Fields

- Kind: Term
- Last checked: 2026-09-17
- Also known as: del(5q); 5q deletion; 5q-; 5q minus; 5q- syndrome; 5q minus syndrome; MDS with isolated del(5q); MDS-5q; isolated del(5q); del 5q MDS; chromosome 5q deletion syndrome; MDS with low blasts and isolated 5q deletion

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Chromosome_5q_deletion_syndrome
- Wikipedia: https://en.wikipedia.org/wiki/Chromosome_5q_deletion_syndrome

## Connected records

- terms: [Cytogenetics and karyotype](https://onco.cc/terms/cytogenetics/), [FISH / ISH (in situ hybridisation)](https://onco.cc/terms/fish/), [IPSS-R and IPSS-M (myelodysplastic syndrome risk scores)](https://onco.cc/terms/ipss-m-ipss-r/), [TP53-mutated (p53-abnormal)](https://onco.cc/terms/tp53-mutated/)
- drugs: [Lenalidomide](https://onco.cc/drugs/lenalidomide/), [Luspatercept](https://onco.cc/drugs/luspatercept/)
- targets: [Cereblon (CRBN)](https://onco.cc/targets/cereblon/)
- cancers: [Higher-risk myelodysplastic syndromes](https://onco.cc/cancers/mds-higher-risk/), [Lower-risk myelodysplastic syndromes](https://onco.cc/cancers/mds-lower-risk/)

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