Pediatric White Blood Cell Disorders: A Parent's Guide to High and Low Counts in Children
Updated: 5 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 17, 2026
Pediatric white blood cell disorders happen when a child has too few white blood cells (leukopenia) or too many (leukocytosis). White blood cells come from bone marrow and fight infections, so a long-term low count raises the risk of infection, while a high count most often signals an infection [1]. Causes range from infections and allergies to medicines, autoimmune conditions, and cancer, and treatment is directed at the underlying cause [1] [2].
Quick Answer
Pediatric white blood cell disorders are conditions in which a child has too few or too many white blood cells, the immune cells that fight infections. A low count, called leukopenia, raises infection risk when it lasts, while a high count, leukocytosis, most often results from infection. Diagnosis relies on history, exam and blood tests, and treatment targets the cause. [1] [2]
What the research says
A very high white blood cell count at diagnosis is seen in a minority of children with acute myeloid leukemia. Among 324 children with newly diagnosed acute myeloid leukemia (AML) treated at one hospital between 1997 and 2017, 49 (15.1%) presented with hyperleukocytosis, defined as a white blood cell count of 100 × 10⁹/L or higher. Infection occurred in 38% of those who had leukapheresis, compared with 0% of those who received low-dose cytarabine, and no early deaths occurred in any group. The authors concluded that low-dose cytarabine appears to be a safe and effective way to lower the count (Christakopoulos et al., Cancer, 2023).
Fever with a low neutrophil count is treated urgently in children with cancer. The 2023 update of the international guideline on fever and neutropenia in children with cancer and stem cell transplant recipients drew on 10 new randomized trials in addition to 69 from earlier guidelines. It includes a good practice statement to start guideline-consistent empiric antibacterial therapy as soon as possible in clinically unstable febrile patients (Lehrnbecher et al., J Clin Oncol, 2023).
Some common antibiotics can lower the neutrophil count. A review of studies in children and adults described drug-induced neutropenia as a well-documented adverse reaction to β-lactam antibiotics, with an incidence of approximately 10% after at least 2 weeks of intravenous therapy. Management centers on stopping the offending drug, and the authors suggest that a β-lactam with a different side chain may be considered later with close laboratory monitoring (Cimino et al., Ann Pharmacother, 2021).
Research summaries are based on article abstracts retrieved from PubMed.
What Are Pediatric White Blood Cell Disorders?
White blood cells, also called leukocytes, are part of the immune system. They are produced in the bone marrow and help the body fight infections. In a pediatric white blood cell disorder, a child has either too few or too many of these cells, and several different conditions can cause the imbalance [1].
A low white blood cell count is called leukopenia. When a low count lasts a long time, it raises the child's risk of infections. A high count is called leukocytosis, and it most often comes from an infection [1].
Term | Meaning | What It Signals |
Leukocytes | White blood cells | Immune cells from bone marrow that fight infections |
Leukopenia | Low white blood cell count | Too few leukocytes in the blood |
Leukocytosis | High white blood cell count | Too many leukocytes in the blood |
What are the five types of white blood cells in children?
Children have five main types of white blood cells, and each type has its own disease-fighting activity. Understanding the five main types helps explain what a lab result may mean [1].
Cell Type | What It Does | When the Count Is Off |
Neutrophils | Fight infections caused by bacteria or fungi. | Too few causes neutropenia. |
Lymphocytes (T cells and B cells) | Mainly protect against viral infections. | Too few causes lymphocytopenia. |
Monocytes | Help rid the body of dead or damaged tissue and support the immune response. | The count can rise or fall. |
Eosinophils | Help with inflammation, parasites, and allergies. | Too many causes eosinophilia. |
Basophils | Play a role in wound healing, asthma, and allergic reactions. This is the least common type. | The count can rise or fall. |
Neutropenia (noo-troe-PEE-nee-uh) means having too few neutrophils. Lymphocytopenia (lim-foe-sie-toe-PEE-nee-uh) means having too few lymphocytes. Eosinophilia (e-o-sin-o-FIL-e-uh) means having too many eosinophils [1].
What are the symptoms of pediatric white blood cell disorders?
Symptoms depend on which type of white blood cell is affected and whether there are too few or too many of them. They might be symptoms of infections, autoimmune conditions (conditions in which the immune system attacks the body's healthy tissues), allergies, or certain cancers [1].
What You Might See | Possible Connection |
Signs of infection | White blood cells fight infections, so counts often shift with illness. |
Autoimmune-type symptoms | The immune system attacks the body’s healthy tissues. |
Allergy symptoms | Eosinophils and basophils help with allergies. |
Signs related to certain cancers | Some cancers and their treatments affect white blood cell counts. |
When should you see a doctor about a child's white blood cell count?
If your child has symptoms that worry you, make an appointment with your child's main healthcare professional [2]. Abnormal blood counts may also be found on tests ordered for another reason. If that happens, follow up with the professional who ordered the test, and ask whether repeat blood counts are needed to monitor the count.
If your child is being treated for cancer and develops a fever, call the care team right away or go to the emergency department, because fever with a low neutrophil count is a medical emergency. Guidelines call for starting antibiotic treatment as soon as possible in children with fever and neutropenia who are clinically unstable [4].
What causes pediatric white blood cell disorders by cell type?
The cause of a pediatric white blood cell disorder depends on which type of white blood cell is affected, which is why diagnosis focuses first on identifying the cell type involved [1].
Affected Cell | Possible Causes |
Neutrophils (too few) | Cancer; conditions that damage bone marrow; certain medicines; infections; other conditions. |
Lymphocytes (too few) | Inherited syndromes; infections; cancer; autoimmune conditions; a side effect of some medicines or other treatments. |
Monocytes (too many) | Infections; cancer; autoimmune diseases; other conditions. |
Monocytes (too few) | Toxins; chemotherapy; other causes. |
Eosinophils (too many) | Allergic reactions; skin conditions; infections with parasites. |
Basophils (too few) | Allergic reactions; infections. |
Basophils (too many) | Certain types of blood cancer; other conditions. |
Inherited syndromes are syndromes passed through families. For eosinophilia, the most common causes are allergic reactions, skin conditions, and parasite infections [1]. Drug-induced neutropenia is also a well-documented reaction to some antibiotics [5].
What are the risk factors for pediatric white blood cell disorders?
The following factors can raise the risk of pediatric white blood cell disorders [1]:
Family history: inherited syndromes can cause cell count problems.
Infections: illness can raise or lower different cell counts.
Cancer: cancer and its treatments can affect the cells made in the bone marrow.
Allergies: allergic reactions affect eosinophils and basophils.
Autoimmune conditions: the body attacks its own cells, which can affect counts.
Certain medicines: some drugs can lower or raise white blood cell counts.
What are the complications of pediatric white blood cell disorders?
The main concern with a long-term low white blood cell count is infection, because the cells that fight infection are in short supply [1]. A high count most often reflects an infection that needs care or another condition that needs treatment [1]. Chemotherapy and some other treatments can also lower counts [1].
Prompt evaluation of abnormal counts and careful follow-up with your child’s healthcare team are the best protection.
How Are Pediatric White Blood Cell Disorders Diagnosed?
Diagnosis involves a detailed medical history and a physical exam. Blood tests are key to diagnosing these disorders, and the healthcare professional may order other tests depending on the suspected cause [2]. A complete blood count (CBC), which measures the number of each type of white blood cell, is the standard blood test. The goal is to identify which cell type is affected, whether the count is high or low, and what is causing the change.
Diagnostic Step | What It Reveals |
Detailed medical history | Family history, medicines, infections, and the pattern of symptoms. |
Physical exam | Signs of infection, allergy, or other conditions. |
Blood tests | The key tests for identifying high or low counts. |
Other tests as needed | Ordered based on the suspected cause. |
How Are Pediatric White Blood Cell Disorders Treated?
Treatment depends on the type of condition caused by the high or low white blood cell count and on the underlying cause. There is no single treatment for all pediatric white blood cell disorders, because the right approach changes with the cause [2].
Treatment Focus | How It Works |
Underlying cause | Treatment is directed at what is changing the cell count. |
Infection treatment | Antibiotics, antiviral medicines, or antifungal medicines may be used for infections. |
Medicine review | Some medicines can change counts, so they may be evaluated and managed safely by the healthcare team. |
When a medicine is contributing to the problem, stopping the offending drug is the cornerstone of management, and the care team weighs whether and when a similar drug can be used again [5].
How should you prepare for a child's white blood cell appointment?
If your child has symptoms that worry you, make an appointment with your child's main healthcare professional. Getting organized ahead of time makes the visit more useful for everyone [2].
What You Can Do
Before the appointment, make a list of:
Your child's symptoms: including any that seem unrelated to the reason for the appointment, and when they began.
Key personal information: major stresses, recent life changes, and family medical history.
All medicines, vitamins, and supplements: everything your child takes, including the dosages.
Questions to ask: your list of questions for your child’s healthcare professional.
Questions to Ask
For pediatric white blood cell disorders, you might ask:
What's the likely cause of my child's symptoms?
What are other possible causes?
What tests does my child need?
Is this condition likely to go away or to last?
What's the best course of action?
Are there restrictions my child needs to follow?
Should I take my child to a specialist?
Are there brochures or other printed material I can have? What websites do you suggest?
Be sure to ask all the questions you have.
What to Expect From Your Doctor
Your child’s healthcare professional may ask you questions such as:
Does your child always have symptoms, or do they come and go?
How bad are the symptoms?
What, if anything, seems to make the symptoms better?
What, if anything, seems to make the symptoms worse?
Conclusion
Pediatric white blood cell disorders are conditions in which a child has too few or too many white blood cells, the immune cells produced by bone marrow that help fight infections. A long-term low count, called leukopenia, raises infection risk, while a high count, called leukocytosis, most often comes from an infection [1]. Causes vary by cell type and include infections, allergies, medicines, autoimmune conditions, and cancer. Diagnosis relies on a detailed history, a physical exam, and blood tests, and treatment is directed at the underlying cause [2].
Your next step: If your child has symptoms that worry you, make an appointment with your child's main healthcare professional. Bring your list of symptoms, medicines, family history, and questions to make the visit count.
Frequently Asked Questions
What are pediatric white blood cell disorders?
Pediatric white blood cell disorders are conditions in which a child has too few or too many white blood cells (leukocytes), the immune cells from bone marrow that fight infections. Several conditions can cause these changes [1].
What is leukopenia?
Leukopenia is a low white blood cell count. A long-term low count raises the risk of infections [1].
What is leukocytosis?
Leukocytosis is a high white blood cell count. It most often is caused by an infection [1].
What is the most common type of white blood cell?
Neutrophils make up more than half of the body's white blood cells. They fight infections caused by bacteria or fungi [1].
What is neutropenia?
Neutropenia means having too few neutrophils, the cells that fight bacterial and fungal infections. It can be caused by cancer, conditions that damage bone marrow, certain medicines, or infections [1].
What causes lymphocytopenia in children?
Lymphocytopenia, a low lymphocyte count, can be caused by inherited syndromes, infections, cancer, autoimmune conditions, or a side effect of some medicines or treatments [1].
What causes eosinophilia?
Allergic reactions, skin conditions, and infections with parasites are the most common causes of too many eosinophils [1].
What are the risk factors for pediatric white blood cell disorders?
Risk factors include family history, infections, cancer, allergies, autoimmune conditions, and certain medicines [1].
How is a pediatric white blood cell disorder diagnosed?
Diagnosis involves a detailed medical history and a physical exam. Blood tests are key, and other tests may be ordered depending on the suspected cause [2].
How is it treated?
Treatment depends on the type of condition caused by the high or low count and on the underlying cause. Treatment for infection might involve antibiotics, antiviral medicines, or antifungal medicines [2].
Can these disorders be prevented?
The causes vary widely, from infections to medicines to inherited syndromes, so no single step prevents them. Care focuses on finding and treating the underlying cause and on telling your child's healthcare professional promptly about worrying symptoms.
What questions should I ask my child's doctor?
Ask about the likely cause of the symptoms, other possible causes, which tests are needed, whether the condition will go away or last, the best course of action, any restrictions, whether a specialist is needed, and what written materials or websites the doctor suggests [2].
Related Resources
External resources for deeper reading:
National Cancer Institute: White Blood Cell — federal definition of white blood cells
American Cancer Society: Neutropenia (Low White Blood Cell Count) — overview of low neutrophil counts
Blood Cancer United (formerly Leukemia & Lymphoma Society): Blood Tests and Urinalysis — patient guide to reading blood counts
Merck Manual Professional Version: Eosinophilia — clinical reference on high eosinophil counts
References
Mayo Clinic Staff. Pediatric white blood cell disorders: Symptoms and causes. Mayo Clinic. May 1, 2025. https://www.mayoclinic.org/diseases-conditions/pediatric-white-blood-cell-disorders/symptoms-causes/syc-20352674
Mayo Clinic Staff. Pediatric white blood cell disorders: Diagnosis and treatment. Mayo Clinic. May 1, 2025. https://www.mayoclinic.org/diseases-conditions/pediatric-white-blood-cell-disorders/diagnosis-treatment/drc-20582387
Christakopoulos GE, Walker KN, Smith J, et al. Clinical characteristics and outcomes of children with newly diagnosed acute myeloid leukemia and hyperleukocytosis managed with different cytoreductive methods. Cancer. 2023;129(12):1873-1884. PMID: 36943896. DOI: 10.1002/cncr.34751
Lehrnbecher T, Robinson PD, Ammann RA, et al. Guideline for the management of fever and neutropenia in pediatric patients with cancer and hematopoietic cell transplantation recipients: 2023 update. J Clin Oncol. 2023;41(9):1774-1785. PMID: 36689694. DOI: 10.1200/JCO.22.02224
Cimino C, Allos BM, Phillips EJ. A review of β-lactam-associated neutropenia and implications for cross-reactivity. Ann Pharmacother. 2021;55(8):1037-1049. PMID: 33215507. DOI: 10.1177/1060028020975646
Medical disclaimer
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have about a medical condition.
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