CNL is a rare type of cancer that causes an increased production of neutrophils. It is a type of myeloproliferative neoplasm (MPN). MPNs are blood cancers that start with problems in a stem cell in the bone marrow.

White blood cells called neutrophils usually work as part of the immune system to help protect the body from infections and disease. When chronic neutrophilic leukemia (CNL) develops, the body produces too many neutrophil cells that do not function properly, resulting in an enlarged spleen or liver. It can progress to acute leukemia.

Many people with CNL have a specific gene mutation known as CSF3R T618I.

CNL is a rare, chronic condition. While there were around 200 reported cases of CNL in 2019, the true incidence of the condition is unknown. On average, people are around age 66 when they receive a diagnosis, and it has a slightly higher incidence in males.

This article examines the symptoms and causes of CNL. It also discusses how doctors diagnose and treat the condition and the outlook for people with CNL.

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CNL may present without any symptoms. As the number of neutrophils in the blood increases, symptoms may develop, including:

The first sign of CNL may be bruising or a feeling of fatigue. A medical professional may find an enlarged spleen during an examination and order blood tests and a bone marrow biopsy if they suspect CNL.

Chromosome analysis may look for genetic mutations often found in conjunction with the condition.

Doctors use the criteria set by the World Health Organization (WHO) to diagnose CNL.

There is no standard treatment for CNL as it is so uncommon. Doctors typically target symptom management and use medications to slow the overproduction of white blood cells. The most commonly used drugs are hydroxyurea and interferon alpha.

Hydroxyurea decreases the number of white blood cells circulating in the bloodstream and shrinks an enlarged spleen. However, some people taking hydroxyurea stop responding to it after it is initially successful.

Interferon alpha overactivates the body’s immune system by slowing the rate at which bone marrow produces white blood cells. Interferon alpha treatment may control white blood cell count in people with CNL.

Sometimes, doctors may advise chemotherapy or targeted agents, including:

The success rate is variable, so they may not always recommend this treatment.

Treatments that address the involvement of CSF3R gene mutations are undergoing study.

For a few people with CNL, allogeneic stem cell transplantation provides successful remission. Researchers are currently studying this treatment further.

The outlook for people with CNL is variable. The median survival time is 23.5 months, and may range from 6 months to more than 20 years.

An ongoing CNL study should significantly impact treatment protocols and potential outcomes.

Risk of transformation to AML

CNL is an aggressive form of leukemia. It can progress to acute myeloid leukemia (AML), a type of cancer that may involve red or white blood cells or platelets.

According to a 2015 review, progression to AML occurs for about 10–20% of people with CNL. The time to transformation is between 3–94 months, with an average time of 21 months.

Although researchers do not know the exact cause of CNL, they have found a link between it and CSF3R genetic mutation. Other genetic mutations, including SETBP1, ASXL1, and TET2, are also suspected as potential contributors to the development of the disease.

There may be an association between the development of CNL and polycythemia vera (PV), a rare blood disorder that results in an increase in all blood cells.

According to one study, there have also been problems with plasma cells in up to 32% of people with CNL.

Communication with a care team is vital to any cancer treatment. Questions to consider asking a doctor may include:

  • What tests do I need?
  • What may the results show?
  • How long will the results take?
  • How rare is CNL?
  • What treatment do I need?
  • How long will treatment last?
  • What are the side effects of treatment?
  • Should there be any dietary changes?
  • Can I work?
  • Are there financial resources available?
  • Where can I access help to deal with my feelings?

CNL is a rare type of cancer that affects the number of neutrophils the bone marrow produces. Neutrophils usually function as part of the immune system, warding off disease and infections.

Currently, there is no standardized treatment protocol. Recommended treatments may include medications that reduce the number of white blood cells, targeted chemotherapy, or, rarely, a stem cell transplant.

CNL is a chronic condition, so the goal of treatment is to manage symptoms. Remission is possible, but the disease is aggressive and may develop into AML.