Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Cancer Health Center

Font Size

Myelodysplastic Syndromes Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Pathologic and Prognostic Systems for Myelodysplastic Syndromes

Myelodysplastic syndromes (MDS) are classified according to features of cellular morphology, etiology, and clinical presentation. The morphological classification of MDS is largely based on the percent of myeloblasts in the bone marrow and blood, the type and degree of myeloid dysplasia, and the presence of ring sideroblasts.[1] The clinical classification of the MDS depends upon whether there is an identifiable etiology and whether the MDS has been treated previously.

Pathologic Systems

The World Health Organization (WHO) classification [2] has supplanted the historic French-American-British (FAB) classification,[1] as shown in Table 1.

Table 1. Myelodysplastic Syndromes: Comparison of the FAB and WHO Classifications

FAB (1982)WHO (2008)
AML = acute myeloid leukemia; FAB = French-American-British classification scheme; MDS = myelodysplastic syndromes; WHO = World Health Organization.
Myelodysplastic Syndromes
Refractory anemia.Refractory anemia.
Refractory cytopenia with multilineage dysplasia. Refractory cytopenia with unilineage dysplasia.
Refractory anemia with ring sideroblasts.Refractory anemia with ring sideroblasts.
Refractory anemia with excess blasts.Refractory anemia with excess blasts -1 and -2.
Myelodysplastic syndrome, unclassifiable.
Myelodysplastic syndrome associated with del(5q).
Reclassified from MDS to:
Refractory anemia with excess blasts in transformation.Acute myeloid leukemia identified as AML with multilineage dysplasia following a myelodysplastic syndrome.
Chronic myelomonocytic leukemia.Myelodysplastic and myeloproliferative diseases.

MDS cellular types and subtypes in either cellular classification scheme have different degrees of disordered hematopoiesis, frequencies of transformation to acute leukemia, and prognoses.

Refractory anemia (RA)

In patients with RA, the myeloid and megakaryocytic series in the bone marrow appear normal, but megaloblastoid erythroid hyperplasia is present. Dysplasia is usually minimal. Marrow blasts are less than 5%, and no peripheral blasts are present. Macrocytic anemia with reticulocytopenia is present in the blood. Transformation to acute leukemia is rare, and median survival varies from 2 years to 5 years in most series. RA accounts for 20% to 30% of all patients with MDS.

Refractory anemia with ring sideroblasts (RARS)

In patients with RARS, the blood and marrow are identical to those in patients with RA, except that at least 15% of marrow red cell precursors are ring sideroblasts. Approximately 10% to 12% of patients present with this type, and prognosis is identical to that of RA. Approximately 1% to 2% of RARS evolve to acute myeloid leukemia (AML).

    Next Article:

    Today on WebMD

    Colorectal cancer cells
    New! I AM Not Cancer Facebook Group
    Lung cancer xray
    See it in pictures, plus read the facts.
    sauteed cherry tomatoes
    Fight cancer one plate at a time.
    Ovarian cancer illustration
    Real Cancer Perspectives
    Jennifer Goodman Linn self-portrait
    what is your cancer risk
    colorectal cancer treatment advances
    breast cancer overview slideshow
    prostate cancer overview
    lung cancer overview slideshow
    ovarian cancer overview slideshow
    Actor Michael Douglas