{"entity":{"id":"del5q","kind":"term","name":"del(5q) (5q- syndrome and lenalidomide response)","aka":["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"],"tldr":"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.","asOf":"2026-09-17","wikipedia":"https://en.wikipedia.org/wiki/Chromosome_5q_deletion_syndrome","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Chromosome_5q_deletion_syndrome"}],"tags":[],"related":["ipss-m-ipss-r","cytogenetics","fish","lenalidomide","cereblon","tp53-mutated","luspatercept"],"cancers":["mds-lower-risk","mds-higher-risk"],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"Biomarkers"},"route":"/terms/del5q/","neighbours":{"term":[{"id":"cytogenetics","kind":"term","name":"Cytogenetics and karyotype","route":"/terms/cytogenetics/"},{"id":"fish","kind":"term","name":"FISH / ISH (in situ hybridisation)","route":"/terms/fish/"},{"id":"ipss-m-ipss-r","kind":"term","name":"IPSS-R and IPSS-M (myelodysplastic syndrome risk scores)","route":"/terms/ipss-m-ipss-r/"},{"id":"tp53-mutated","kind":"term","name":"TP53-mutated (p53-abnormal)","route":"/terms/tp53-mutated/"}],"drug":[{"id":"lenalidomide","kind":"drug","name":"Lenalidomide","route":"/drugs/lenalidomide/"},{"id":"luspatercept","kind":"drug","name":"Luspatercept","route":"/drugs/luspatercept/"}],"target":[{"id":"cereblon","kind":"target","name":"Cereblon (CRBN)","route":"/targets/cereblon/"}],"cancer":[{"id":"mds-higher-risk","kind":"cancer","name":"Higher-risk myelodysplastic syndromes","route":"/cancers/mds-higher-risk/"},{"id":"mds-lower-risk","kind":"cancer","name":"Lower-risk myelodysplastic syndromes","route":"/cancers/mds-lower-risk/"}]}}