When people have abnormally low levels of white blood cells (called neutrophils), they have a condition known as neutropenia. Without sufficient levels of neutrophils, which protect the body from infection, the immune system can’t function properly. For this reason, people with neutropenia may have frequent infections, some of which could be life-threatening. Depending on the cause, some people may have few symptoms—or even no symptoms at all.

Neutropenia can be caused by genetic conditions, infections, cancer, autoimmune diseases, medications, and/or a nutritional deficiency. People may have acute (or short-term) or chronic (or long-term) forms of the condition.

Although neutropenia can affect anyone, children and older adults are diagnosed with the condition more often than adults. And women are diagnosed about five times more often than men.

The good news is that there are treatments available to improve neutropenia, as well as to treat some of its underlying causes.

Neutropenia is a condition that arises when a person has very low levels of certain white blood cells (called neutrophils) that fight infection. These cells are an essential part of the body’s immune system. A person who has too few may become ill frequently.

A healthy adult may have up to 8,000 neutrophils per microliter of blood. A person with fewer than 1,500 neutrophils will be diagnosed with neutropenia. Having 1,000 to 1,500 neutrophils is considered mild neutropenia, while 500 to 1,000 is considered moderate. People with fewer than 500 neutrophils per microliter have severe neutropenia. Typically, only people with severe neutropenia are at risk of life-threatening infections.

Several conditions may significantly lower white blood cell levels, causing neutropenia, such as:

• Infections, including mononucleosis, measles, Epstein-Barr virus, malaria, and tuberculosis
• Hepatitis
• HIV
• Lupus, rheumatoid arthritis, Felty syndrome, or other autoimmune diseases
• An enlarged or overactive spleen
• Sepsis
• Leukemia
• Lymphoma
• Metastatic (advanced) cancer
• Aplastic anemia
• Fanconi anemia
• Kostmann syndrome, Chediak-Higashi syndrome, or other inherited conditions
• Inherited CSF3R gene mutations
• Vitamin B12 deficiency
• Folate deficiency

Certain medications may also cause neutropenia, including:

• Anti-seizure medicine
• Some antipsychotic medications, like clozapine
• Certain antibiotics
• Antifungal medication
• Thyroid medication
• Quinine for malaria
• Rituximab, a monoclonal antibody
• Certain blood thinners, like ticlopidine
• Diuretics
• Some cardiovascular drugs
• Non-steroidal anti-inflammatory drugs (NSAIDs)
• H2 blockers for acid reflux
• Benzodiazepines for anxiety
• Certain antidepressants
• Cancer treatments, such as chemotherapy or radiation therapy

Babies who develop neutropenia may have:

• Been born prematurely
• Been born small for their gestational age
• Been born to a mother who had preeclampsia during pregnancy
• Received a transfer of antibodies from the mother, through the placenta, that caused the condition

There are no hallmark symptoms associated with the condition. Symptoms associated with neutropenia can be similar to symptoms of infection:

• Fever
• Swollen lymph nodes
• Inflammation of the gums (gingivitis) or mouth sores
• Rash

Sometimes, neutropenia is found during routine bloodwork at an annual doctor’s visit. However, doctors may suspect neutropenia simply because a patient has frequent infections.

A medical history, physical exam, and diagnostic tests can be used to diagnose neutropenia.

During the medical history part of the appointment, tell your doctor about your history (or your child’s history) of illness and infection, with details about how frequently the infections have occurred. If you or your child have had leukemia or other types of cancer, or if you’re receiving chemotherapy or radiation treatments, share that information with the doctor. They may also ask if you or your child have used medications associated with neutropenia.

During a physical exam, the doctor may look for signs of neutropenia, including swollen lymph nodes and an enlarged spleen. They may look for evidence of past or present skin infections, which are more likely to occur in someone with neutropenia.

The following tests may also be used to diagnose the condition:

• Blood tests, including a complete blood count (CBC), which reveals the number of neutrophils present in the blood, and a blood smear, which looks at the cells under a microscope for abnormalities
• Bone marrow aspiration (which entails removing a small sample of liquid) or biopsy (removing a small sample of tissue) for analysis
• Urine tests, to rule out other conditions
• Chest X-ray, to rule out other conditions
• Other imaging tests, such as a computed tomography (CT) scan, to rule out other conditions

Different treatments for neutropenia are available, depending on its cause. Mild neutropenia may not need to be treated. Neutropenia caused by another condition, for instance, may improve if the patient receives treatment for the underlying condition. Medication-induced neutropenia may improve if the patient is switched to a different medication.

In general, treatments for neutropenia include:

• Antibiotics, which fight infection in the body when there are too few neutrophils present
• Filgrastim, an injected medication that stimulates the bone marrow to produce more neutrophils
• Corticosteroids, which may be an effective treatment for neutropenia caused by an autoimmune disorder
• Antithymocyte globulin, an immunosuppressant, which may be appropriate when a patient has neutropenia caused by aplastic anemia
• A bone marrow or stem cell transplant, which may be recommended when neutropenia is caused by leukemia, aplastic anemia, or other conditions

Patients with severe neutropenia and a fever should be admitted to the hospital for immediate treatment; the infection may be life-threatening.

When neutropenia is caused by another condition, such as leukemia, the patient’s prognosis depends upon the prognosis of that condition.

People with acute neutropenia may recover after receiving treatment. Those with mild neutropenia may never require treatment, and the condition may resolve on its own. Some may require long-term monitoring and treatments.

“A diagnosis of neutropenia can be scary for patients, knowing that there are many potential causes and not knowing right away if it is serious or whether a fever might mean a severe infection,” says Aron Flagg, MD, a Yale Medicine pediatric hematologist/oncologist. “Pediatric and adult hematologists at Yale are experts in diagnosing and treating all forms of neutropenia and will work quickly to provide answers. Fortunately, very good treatment options are available for most patients with neutropenia.”