Juvenile myelomonocytic leukemia (JMML), also known as juvenile chronic myelogenous leukemia (JCML), is a rare cancer of the blood that affects young children under the age of 4.1 It occurs when types of white blood cells (WBCs) called monocytes and myelocytes do not mature normally or when there is an uncontrollable growth of these two types of white blood cells. The immature cells are known as blasts.
This rare cancerous condition can occur spontaneously or be associated with other genetic disorders. According to Cancer Research UK, it has been found that JMML occurs slightly more often in boys than in girls.2 The Leukemia & Lymphoma Society estimates that around 50 children in the U.S. are diagnosed with JMML each year, accounting for 1% to 2% of all childhood leukemia cases.3
Symptoms of Juvenile Myelomonocytic Leukemia
Children with JMML may experience the following symptoms:
- Anemia: Characterized by increased heart rate, fatigue, paleness, and the need for more naps due to a lack of normal red blood cells.
- Recurrent Infections: Symptoms include fatigue and fever, with a longer recovery time.
- Breathing Difficulties: Leukemia cells in the thymus gland can cause wheezing or coughing, requiring emergency medical attention.
- Swollen Lymph Nodes: Often found in the chest, neck, underarms, and groin, indicating a buildup of leukemia cells.
- Bone and Joint Pain: Caused by overcrowding of the bone marrow with blasts.
- Abdominal Pain: Occurs as leukemia cells accumulate in the liver, spleen, or kidneys, leading to organ enlargement.
- Bleeding and/or Bruising: Results from a low platelet count, making bleeding and bruising more frequent.
Causes and Risk Factors for Juvenile Myelomonocytic Leukemia
The exact cause of most cases of childhood leukemia, including JMML, remains unclear. However, some genetic disorders have been linked to an increased risk. For example, approximately 15% of children with JMML have neurofibromatosis type 1.5 Children with Noonan syndrome are also at an increased risk. Additionally, excessive alcohol consumption during pregnancy may elevate the risk of the child developing leukemia.
Diagnosing Juvenile Myelomonocytic Leukemia
Diagnosis may involve a variety of tests, including:
- Physical Examination: To check for symptoms like an enlarged spleen or swollen lymph nodes.
- Blood Tests: Including a complete blood count and blood smear.
- Bone Marrow Aspiration and Biopsy: To examine the bone marrow cells.
- Lymph Node Biopsy: To analyze the cells in swollen lymph nodes.
- Lumbar Puncture: To check the cerebrospinal fluid for leukemia cells.
- Genetic Tests: To identify any DNA changes indicating leukemia.
- Imaging Tests: Such as chest X-rays, CT scans, and MRIs, though they are less commonly used for diagnosis.
Stages and Treatment of Juvenile Myelomonocytic Leukemia
While JMML does not have a standard staging system, the progression of the disease can be categorized into various phases such as untreated, remission, minimal residual disease, active disease, recurrent disease, refractory disease, and central nervous system disease.
Treatment mainly revolves around stem cell transplantation, which is currently the only known cure for JMML. About half of the patients achieve long-term remission with this treatment, although relapses are common. Chemotherapy is also used, primarily to manage symptoms and prepare for stem cell transplantation.
