del (5q) solely in Myelodysplastic syndrome

2016-10-01   Robert S. Ohgami  , Nahid Shahmarvand  

1.Department of Pathology, Stanford University, Stanford, CA, USA; ROhgami@stanfordhealthcare.org

Abstract

Review on Myelodysplastic syndrome with isolated deletion of 5q

Clinics and Pathology

Disease

Myelodysplastic syndrome (MDS) with isolated deletion of chromosome 5q is part of a group of clonal disorders in myeloid stem cells with ineffective hematopoiesis which is manifested by morphologic dysplasia in hematopoietic cells and single or bilineage cytopenia(s). It is the only MDS subtype defined cytogenetically in the World Health Organization classification system.

Phenotype stem cell origin

Myeloid stem cell.

Epidemiology

MDS with isolated del(5q) is present in

Clinics

Patients suffering from MDS with isolated del(5q) present with a macrocytic anemia, normal or increased platelet count and absence of significant neutropenia in their peripheral blood. The incidence of bleeding and infections is therefore low in these patients because of the absence of significant neutropenia and thrombocytopenia. Blood transfusion dependency is seen in patients with severe anemia at diagnosis but also can develop in other patients (Germing et al., 2012). According to the Revised International Prognostic Scoring System (IPSS-R), MDS with isolated del(5q) are defined as Low- or Intermediate -1- risk subtypes and usually have an indolent course.
Atlas Image
Figure 1: An example of a typical hypolobated micromegakaryocyte in a bone marrow aspirate smear. (Wright-Giemsa)

Pathology

The bone marrow is characterized by an increase in the number of small megakaryocytes with monolobulated and bilobulated nuclei. There are less than 1% blasts in the peripheral blood and less than 5% blasts in the bone marrow and Auer Rods are absent (Arber et al., 2016).

Treatment

MDS patients with isolated del(5q) have a favorable prognosis and the majority of patients respond well to treatment with lenalidomide.

Prognosis

This subtype of MDS has a favorable prognosis. The exception is when this disease is associated with mutations in TP53.

Cytogenetics

Atlas Image
Figure 2: The karyotype in a case of MDS with isolated del(5q) showing 46,XX,del(5)(q22q35). Image courtesy of Dana Bangs, CG(ASCP), Stanford University.

Cytogenetics morphological

As its name implies, in this entity there is interstitial deletion of part of the long arm of chromosome 5 involving 5q31-5q33. MDS with isolated del(5q) can still be diagnosed if there is 1 additional cytogenetic abnormality besides del(5q) if there is no adverse effect of that abnormality, as such, this excludes monosomy 7 or del 7(q) for instance (Arber et al., 2016).

Cytogenetics molecular

The gene specific for the defect seen in MDS with isolated del(5q) has been identified by RNA interference screening to be RPS14 (Pellagatti et al., 2008). In addition, while patients with MDS with isolated del(5q) classically have a favorable prognosis, the presence of a TP53 mutation is of particular importance, this mutation predicts for poorer prognosis and higher risk of transformation to AML (Mallo et al.,2013).

Genes Involved and Proteins

Gene name
RPS14 (ribosomal protein S14)
Location
5q33.1
Protein description
RPS14 is a ribosomal gene located in commonly deleted region (CDR) of 5q. It encodes for a protein required for maturation of 40S ribosomal subunits. Patients with MDS with del(5q) are haploinsufficient for RPS14 which leads to impairment of ribosome biogenesis and subsequent reduction of protein translation.
Gene name
TP53 (Tumour protein p53 (Li-Fraumeni syndrome))
Location
17p13.1
Protein description
The TP53 gene encodes for the tumor suppressor protein p53. In the presence of DNA -damage p53 may be activated to fix the damage, or if the damage cannot be repaired p53 prevents the cell from dividing and signals the cell to undergo apoptosis.

Article Bibliography

Pubmed IDLast YearTitleAuthors
266377362015Reclassifying myelodysplastic syndromes: what's where in the new WHO and why.Arber DA et al
270692542016The 2016 revision to the World Health Organization classification of myeloid neoplasms and acute leukemia.Arber DA et al
248810412014Clinical and genetic predictors of prognosis in myelodysplastic syndromes.Bejar R et al
222899902012Survival, prognostic factors and rates of leukemic transformation in 381 untreated patients with MDS and del(5q): a multicenter study.Germing U et al
215190102011TP53 mutations in low-risk myelodysplastic syndromes with del(5q) predict disease progression.Jädersten M et al
208820452011Impact of adjunct cytogenetic abnormalities for prognostic stratification in patients with myelodysplastic syndrome and deletion 5q.Mallo M et al
236146822013Response to lenalidomide in myelodysplastic syndromes with del(5q): influence of cytogenetics and mutations.Mallo M et al
215237972011Isolated del(5q) in myeloid malignancies: clinicopathologic and molecular features in 143 consecutive patients.Patnaik MM et al
184770452008Haploinsufficiency of RPS14 in 5q- syndrome is associated with deregulation of ribosomal- and translation-related genes.Pellagatti A et al
246825122014p53 protein expression independently predicts outcome in patients with lower-risk myelodysplastic syndromes with del(5q).Saft L et al

Summary

Atlas Image
del (5q) Partial karyotypes with del(5q) (A). Hybridization with Vysis LSI CSF1R (5q33-34)/5p15.2 and Vysis EGR1(5q31)/5p15.2 probes (Abbott molecular, US) showing 2 red and 2 green signals on normal metaphase (B) and showing deletions of various sizes involving EGRI and CSFR1 (missing red signals) (C-I) - Courtesy Adriana Zamecnikova.

Citation

Robert S. Ohgami ; Nahid Shahmarvand

del (5q) solely in Myelodysplastic syndrome

Atlas Genet Cytogenet Oncol Haematol. 2016-10-01

Online version: http://atlasgeneticsoncology.org/haematological/1134/deep-insight-explorer/gene-fusions-explorer/js/lib/zoomerang.js