CMML
Meaning of CMML: A marrow disorder sitting between two families of blood disease, defined by a stubbornly high count of one white cell type.
Definition of CMML
CMML stands for chronic myelomonocytic leukemia, a bone marrow cancer in which monocytes, one type of white blood cell, are produced in excess and persist in the blood over months. The marrow also fails to make normal cells properly, so anemia and low platelets are common. It occurs mainly in older adults and can transform into an acute leukemia.
Why is it classified as an overlap disorder?
Blood cancers of the marrow have traditionally split into two families. In one, the marrow produces cells that are too few and poorly formed. In the other, it produces too many of a mature cell type. This condition does both at once, which is why classification systems place it in a category of its own between them.
| Myelodysplastic feature | Myeloproliferative feature | |
|---|---|---|
| What is seen | Anemia, low platelets, abnormal cell shapes | Persistently high monocyte count, enlarged spleen |
| Consequence | Fatigue, infection, bruising | Abdominal fullness, weight loss, sweats |
How is it diagnosed?
The starting point is a monocyte count that stays raised for months without an infection or inflammatory illness to explain it, since monocytes rise for many ordinary reasons. A bone marrow sample is then examined for abnormal cell shapes and for the proportion of immature blast cells, which determines the subgroup. Genetic testing is central, and one result is decisive: this condition does not carry the Philadelphia chromosome. Its presence would instead indicate chronic myeloid leukemia, a different disease with a different treatment. Several recurring gene mutations are found, and some carry prognostic weight.
What happens over time?
The course varies widely. Some people remain stable for years with a raised count and few symptoms. Others develop worsening anemia requiring transfusions, an enlarging spleen, or a rising proportion of blast cells. Transformation to acute myeloid leukemia occurs in a substantial minority and is the main cause of death. Scoring systems that combine blood counts, blast percentage and genetic findings are used to estimate the likely course. Stem cell transplantation is the only approach that can eliminate the disease, and its suitability turns on age and general health, which limits it in a condition of later life. Other treatment aims to control counts and symptoms.
Also known as
Used in a sentence
Persistent monocytosis with dysplastic changes on the marrow aspirate supported a diagnosis of CMML.
Good to know
A raised monocyte count has many ordinary causes, and the diagnosis requires persistence over months plus marrow findings; absence of the Philadelphia chromosome separates it from chronic myeloid leukemia.