What Is Myelodysplastic Syndrome (MDS)? Understanding Symptoms, Types, and Progression

Myelodysplastic syndrome (MDS), once commonly referred to as "pre-leukemia," is a group of diverse bone marrow disorders characterized by the body's inability to produce healthy, fully functioning blood cells. This condition originates in the hematopoietic stem cells—those responsible for generating red blood cells, white blood cells, and platelets. When these stem cells become genetically altered or damaged, they begin producing abnormal or immature blood cells that fail to mature properly, leading to ineffective hematopoiesis.

Understanding the Biology Behind MDS

At its core, MDS is a clonal disorder, meaning it arises from a single mutated stem cell that multiplies and dominates the bone marrow environment. This genetic mutation disrupts normal blood cell development, resulting in dysplasia—abnormal shape, size, or appearance of blood cells—and cytopenias, which are low blood cell counts across one or more lineages. Patients often present with anemia (low red blood cells), neutropenia (low white blood cells), or thrombocytopenia (low platelets), each contributing to symptoms like fatigue, increased infection risk, and easy bruising or bleeding.

Why MDS Was Once Called Pre-Leukemia

The term "pre-leukemia" was historically used because a significant subset of MDS cases can progress to acute myeloid leukemia (AML)—a fast-growing and aggressive blood cancer. However, not all types of MDS carry the same risk. The progression rate varies widely depending on the specific subtype, genetic markers, and overall patient health.

Diverse Subtypes and Risk Levels

One of the defining features of MDS is its high degree of heterogeneity. The World Health Organization (WHO) classifies MDS into several subtypes based on factors such as the number of dysplastic cell lines, blast percentage in the bone marrow, and specific chromosomal abnormalities. Some forms, like lower-risk MDS (e.g., refractory cytopenia with unilineage dysplasia), may remain stable for years with minimal intervention. Others, such as higher-risk MDS with excess blasts, can rapidly evolve into AML within months.

Prognostic Factors and Treatment Outlook

Risk stratification tools, such as the Revised International Prognostic Scoring System (IPSS-R), help clinicians predict disease behavior and tailor treatment plans. These assessments consider variables including hemoglobin levels, cytogenetic profile, and bone marrow blast count. While some patients may only require regular monitoring and supportive care like blood transfusions, others might benefit from immunomodulatory drugs, hypomethylating agents, or even allogeneic stem cell transplantation—the only potentially curative option available today.

Advancements in genomic testing and targeted therapies continue to improve outcomes for MDS patients. Early diagnosis, personalized treatment strategies, and ongoing research are key to managing this complex group of disorders and enhancing quality of life.