Various health conditions and treatments can cause neutropenia. Depending on the cause, neutropenia happens because neutrophils are destroyed, made in fewer numbers or stored in an irregular way.

Causes of neutropenia include the following:

Cancer and cancer treatments

Certain cancers can cause neutropenia. These include:

1. Leukemia
2. Lymphoma
3. Multiple myeloma

Various cancer treatments also can cause neutropenia. For instance, chemotherapy and radiation can destroy neutrophils and other healthy cells along with cancer cells.

1. Bone marrow transplant
2. Chemotherapy
3. Radiation therapy
4. Targeted therapy.

Medicines

1. Medicines to treat overactive thyroid such as methimazole and propylthiouracil.
2. Antibiotics such as nafcillin, penicillin G and oxacillin.
3. Antiviral medicines such as acyclovir (Sitavig, Zovirax), ganciclovir (Ganzyk-RTU, Valcyte, others) and oseltamivir (Tamiflu).
4. Anti-inflammatory medicines for conditions such as ulcerative colitis or rheumatoid arthritis. These include sulfasalazine (Azulfidine), leflunomide (Arava) and methotrexate (Rasuvo, Trexall, others).
5. Antipsychotic medicines such as clozapine (Clozaril, Versacloz) and chlorpromazine.
6. Medicines to treat irregular heart rhythms, including quinidine and procainamide.
7. Medicines to treat some skin conditions, including dapsone (Aczone) and isotretinoin (Absorica, Amnesteem, others).
8. A veterinary drug called levamisole that's not approved for human use in the United States but may be mixed in with cocaine.

Infections

1. Chickenpox
2. Coronavirus disease 2019 (COVID-19)
3. Cytomegalovirus (CMV) infection
4. Epstein-Barr virus
5. Hepatitis A
6. Hepatitis B
7. Hepatitis C
8. HIV/AIDS
9. Measles
10. Rubella
11. Salmonella infection
12. Sepsis (an overwhelming bloodstream infection)

Autoimmune diseases

1. Granulomatosis with polyangiitis
2. Lupus
3. Rheumatoid arthritis

Bone marrow disorders

1. Aplastic anemia
2. Myelodysplastic syndromes
3. Myelofibrosis

Other causes

1. Genetic conditions such as Fanconi anemia, Kostmann syndrome and Shwachman-Diamond syndrome.
2. Unknown reasons called chronic idiopathic neutropenia.
3. Low levels of nutrients such as vitamin B-12, copper or folate.
4. Some conditions of the spleen.

People can have neutropenia without a higher risk of infection. This is known as benign neutropenia.