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GERICLINICS

GeriQBank · Paper III · Q15

WHO Classification & Diagnostic Criteria of MDS, and its Differentials

Very High YieldAsked ×515-mark essay + 7-mark note
Topic
Haematology, Oncology & Screening
Chapter
Haematology
Years asked
Not recorded in the source
Frequency
Set 5× in Paper III and Paper IV (2009–2025)

As set in the university papers — 2 wordings

  • Myelodysplastic syndrome — classification, etiology, clinical features, differential diagnosis, investigations and treatment in the elderly.

    Paper III · Haematology & Oncology · asked ×3 · 15-mark essay + 7-mark note · see in paper list

  • Myelodysplastic syndrome — WHO classification and distinguishing features of each class; diagnostic criteria and the differentials one has to consider.

    Paper IV · Oncology, Haematology & Cancer Screening · asked ×2 · 7-mark note · see in paper list

Answer framework

  1. Cytopenia thresholds — haemoglobin, platelets, neutrophils
  2. WHO 2016 classification — table of subtypes by dysplastic lineages, ring sideroblasts and blasts; the AML cut-off; 5q− syndrome
  3. Diagnostic criteria (IWG/NCCN) — two prerequisites plus one decisive criterion
  4. Differential diagnosis — reversible causes of dysplasia; CHIP, ICUS and CCUS; CMML and other marrow disorders
  5. Recent updates — WHO-HAEM5 (2022) groups, ICC, IPSS-M

An exam answer plan drawn from the detailed answer below. Use it to attempt the question first.

Detailed answer

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Attempt it firstOutline your answer as a 15-mark essay + 7-mark note before revealing it — definition, causes, evaluation, management and the geriatric angle.Reveal answer

Short revision answer

  • Cytopenia thresholds: haemoglobin <10 g/dL, platelets <1,00,000/µL, ANC <1800/µL.
  • WHO 2016 subtypes: MDS-SLD, MDS-RS (ring sideroblasts ≥15%, or ≥5% with SF3B1), MDS-MLD, MDS-EB-1 (blasts PB 2–4% or BM 5–9%), MDS-EB-2 (PB 5–19% or BM 10–19%, or Auer rods) and MDS del(5q).
  • Blasts ≥20% define AML.
  • 5q− syndrome: macrocytic anaemia with normal or increased platelets and hypolobated megakaryocytes.
  • Diagnosis (IWG/NCCN): stable cytopenia for ≥6 months (≥2 with a specific karyotype or bilineage dysplasia) and exclusion of other causes, plus one of: dysplasia in ≥10% of a lineage, blasts 5–19%, or an MDS-associated karyotype (del5q, del20q, +8, −7/del7q).
  • Dysplasia alone does not establish MDS: exclude B12 or folate deficiency, hypothyroidism, EBV/HIV, alcohol, chemotherapy and benzene.
  • CHIP has mutations without cytopenia; ICUS has cytopenia without mutations; CCUS has both, and up to 80% progress in 5 years.
  • Splenomegaly is unusual and suggests CMML.
  • WHO-HAEM5 (2022): "myelodysplastic neoplasms", genetically defined (MDS-5q, MDS-SF3B1, MDS-biTP53) or morphologically defined (MDS-LB, MDS-h, MDS-IB1/IB2, MDS-f). NPM1-mutated cases are AML; IPSS-M replaces IPSS-R.

Condensed by GeriClinics from the detailed answer below, with no new facts added.

Exceptionally well covered: Pathy's Ch. 26/27, Tables 26.1–26.4 and 27.1 — directly quotable.

High-Yield Points

Cytopenia Thresholds (Table 26.1)

Parameter Threshold

Haemoglobin <10 g/dL

Platelets <1,00,000/µL

ANC <1800/µL

WHO 2016 Classification — Full Table

Subtype Dysplastic lineages Ring sideroblasts Blasts MDS-SLD 1 <15% (<5% if SF3B1+) PB<1%, BM<5% MDS-RS 1–3 ≥15% (≥5% if SF3B1+) PB<1%, BM<5% MDS-MLD 2–3 Variable PB<1%, BM<5% MDS-EB-1 0–3 Any PB 2–4% or BM 5–9% MDS-EB-2 0–3 Any PB 5–19% or BM 10–19%, or Auer rods MDS del(5q) 1–3 Any PB<1%, BM<5% Blast-count denominator redefined (2016) to include ALL nucleated marrow cells. ≥20% blasts defines AML (vs MDS-EB-2's ceiling of 19%). 5q− syndrome: macrocytic anaemia with NORMAL/INCREASED platelets, hypolobated megakaryocytes.

IWG/NCCN Diagnostic Criteria

Two prerequisites: (1) stable cytopenia ≥6 months (or ≥2 with specific karyotype/bilineage dysplasia); (2) exclusion of other causes.

Plus ≥1 of: dysplasia ≥10% of a lineage; blasts 5–19%; MDS-associated karyotype (del5q, del20q, +8, −7/del7q).

Differential Diagnosis

"Dysplasia in the marrow is NOT sufficient to establish myelodysplasia" (Pathy's, verbatim). Exclude: B12/folate deficiency, hypothyroidism, EBV/HIV, ethanol, chemotherapy, benzene.

Feature CHIP ICUS CCUS MDS

Cytopenias No Yes Yes Yes

Dysplasia No Minimal Minimal >10% of a lineage

Somatic mutations Yes (VAF≥2%) No Up to 36% Up to 85% 5-yr progression 0.5–1%/yr Up to 10% Up to 80% — Splenomegaly is unusual in MDS — suggests CMML if present. Other differentials: PNH, aplastic anaemia, congenital neutropenia, marrow infiltration by carcinoma/lymphoma.

Latest Updates (2023–Present)

WHO-HAEM5 (2022) renamed "myelodysplastic neoplasms" — two groups:

Group Entity Key criteria

Genetically defined MDS-5q del(5q) alone or +1 other (except −7/del7q)

MDS-SF3B1 SF3B1 mutation ALONE defines it — RS threshold removed MDS-biTP53 (NEW) ≥2 TP53 mutations, or 1 + copy-number loss/cnLOH MD Geriatrics – Haematology Compendium Page 29 of 34 Morphologically defined MDS-LB <5% BM, <2% PB blasts MDS-h (NEW) Hypoplastic marrow MDS-IB1/IB2 Replaces MDS-EB-1/EB-2 MDS-f (NEW) Increased blasts + fibrosis NPM1-mutated cases now reclassified as AML regardless of blast count. ICC creates separate "MDS/AML" for 10–19% blasts (WHO calls this MDS-IB2). IPSS-M (31-gene molecular score) supersedes IPSS-R.

Current Practice Update

Domain Pathy's (WHO 2016) WHO-HAEM5 (2022)

Ring sideroblasts ≥15% defines MDS-RS SF3B1 mutation alone defines the entity Hypoplastic MDS Morphological variant, 15–20% MDS-h — formal WHO category NPM1-mutated Classified by blast % Automatically AML regardless of blast count Prognostic score IPSS/IPSS-R IPSS-M is the reference standard MD Geriatrics – Haematology Compendium Page 30 of 34

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