Leukopenia
Synonyms and keywords: Deficiency in WBC, deficiency in white blood cells, deficiency in leukocytes, low WBC, low white blood cells, low leukocytes, neutrophilic leukopenia, neutrophilic leukocytopenia, neutrophilic leucopenia, neutrophilic leucocytopenia, neutropenia, eosinophilic leukopenia, eosinophilic leukocytopenia, eosinophilic leucopenia, eosinophilic leucocytopenia, eosinophilopenia, basophilic leukopenia, basophilic leukocytopenia, basophilic leucopenia, basophilic leucocytopenia, basophilopenia, leukocytopenia, leucopenia, leukopaenia, lymphopenia, lymphocytopenia

# Overview
Deficiency of absolute number of leukocytes, which may be granulocytes (neutrophils, eosinophils, basophils) or lymphocytes (T-cells, B-cells).  The majority of cases of leukopenia are actually neutropenia since neutrophils constitute the majority of leukocytes.  As the principal function of white cells is to combat infection, a decrease in the number of these cells can place patients at increased risk for infection.  In pancytopenia, the other cell types in the blood (red blood cells and platelets) are similarly affected.  Neutropenia is a decrease in the number of circulating neutrophil granulocytes, the most abundant white blood cells. The terms leukopenia and neutropenia may occasionally be used interchangeably, as the neutrophil count is the most important indicator of infection risk.  However, neutropenia is more properly considered a subset of leukopenia as a whole.  Low white cell counts are associated with chemotherapy, radiation therapy, leukemia (as malignant cells overwhelm the bone marrow), myelofibrosis and aplastic anemia (failure of white and red cell creation, along with poor platelet production).  In addition, many common medications can cause leukopenia. Other causes of low white blood cell count include: Influenza, systemic lupus erythematosus, typhus, malaria, HIV, tuberculosis, dengue, Rickettsial infections, enlargement of the spleen, folate deficiencies and sepsis. Many other causes exist.  Leukopenia can be identified with a complete blood count.

# Classification

# Causes

## Causes by Organ System

## Causes in Alphabetical Order
- Acute cholinergic dysautonomia
- Aflibercept
- Alcoholism
- Alimemazine
- Altretamine
- Aminosalicylic acid
- Amoxicillin
- Aplastic anemia
- Autoimmune diseases
- Azacitidine
- Banti syndrome
- Benign familial neutropenia
- Benzene
- Bone marrow damage
- Brucellosis
- Bullis fever syndrome
- Cachexia
- Capreomycin sulfate
- Carboplatin
- Cefaclor
- Cefotaxime sodium
- Cefpodoxime
- Ceftazidime
- Certolizumab pegol
- Chemotherapy
- Chickenpox
- Chlorpropamide
- Chromosome 8, mosaic trisomy
- Cisplatin
- Clobazam
- Cyclic neutropenia
- Cyclophosphamide
- Cytarabine
- Dacarbazine
- Dactinomycin
- Degenerative and inflammatory vasculopathies
- Dexrazoxane
- Diethylpropion
- Diphtheria
- Diuretics
- Docetaxel
- Doxorubicin hydrochloride
- Drug-induced granulocytopenias
- Ehrlichia ewingii
- Epirubicin hydrochloride
- Epstein-barr virus
- Ethosuximide
- Exanthema subitum
- Fanconi pancytopenia
- Febuxostat
- Felbamate
- Felty syndrome
- Flavoxate
- Flurazepam hydrochloride
- Flurbiprofen
- Folate malabsorption, hereditary
- Folic acid deficiency
- Foscarnet sodium
- Fulvestrant
- Gaucher disease type 3
- Gemifloxacin mesylate
- Ghosal syndrome
- Guanidine
- Haemodialysis
- Heartland virus
- Heavy-chain diseases
- Herbal agent overdose
- Hiv
- Homologous wasting disease
- Hydroxychloroquine
- Hyperdibasic aminoaciduria type 2
- Hyperglobulia
- Hypersplenism
- Hypopituitarism
- Hypothyroidism
- Idiopathic
- Ifosfamide
- Infection
- Infectious mononucleosis
- Infectious hepatitis
- Influenza
- Interleukin 2
- Irinotecan hydrochloride
- Iron deficiency anemia
- Junin virus
- Kala-azar
- Korovnikov syndrome
- Kostmann syndrome
- Leishmaniasis
- Lenalidomide
- Leukemia
- Lincomycin hydrochloride
- Lipid storage disease
- Liver disease
- Lomustine
- Lorcaserin
- Loxapine
- Lupus
- Lymphocytopenia
- Malaria
- Malignant lymphomas
- Mastocytosis
- Mayapple poisoning
- Megaloblastic anemia
- Megestrol
- Melphalan
- Mercaptopurine
- Meropenem
- Metaxalone
- Methocarbamol
- Methylmalonic acidemia
- Milnacipran hydrochloride
- Mitomycin c
- Monosodium methanarsenate
- Mycophenolate
- Myelodysplasia
- Myeloproliferative disorders
- Nabilone
- Neutropenia
- Nilutamide
- Nitisinone
- Nitrous oxide
- Nutrition deficiency
- O'higgins disease
- Olanzapine
- Olaparib
- Olsalazine
- Ornithosis
- Osteomyelosclerosis
- Oxaprozin
- Oxazepam
- Oxcarbazepine
- Paclitaxel
- Palbociclib
- Paraproteinemia
- Paratyphus
- Parvovirus b19
- Penicillamine
- Pergolide
- Pernicious anemia
- Perphenazine
- Pertuzumab
- Poliomyelitis
- Pramipexole
- Primaquine phosphate
- Primary and secondary varicosis
- Probenecid
- Promethazine
- Pyridoxamine 5-prime-phosphate oxidase deficiency
- Pyrimethamine
- Rabeprazole
- Radiotherapy
- Radium chloride
- Refractory anaemia with ringed sideroblasts
- Repaglinide
- Rheumatoid arthritis
- Rickettsial infection
- Rifampin
- Romidepsin
- Rufinamide
- Sabia virus
- Sars
- Septicaemia
- Sirolimus
- Sjogren's syndrome
- Spironolactone
- Spleen disease
- Streptozocin
- Strontium chloride
- Sulindac
- Systemic lupus erythematosus
- Tamoxifen
- Teniposide
- Thioguanine
- Thiotepa
- Thiothixene
- Thyrotoxicosis
- Tiagabine
- Tick borne encephalitis
- Tolazamide
- Tolbutamide
- Toremifene
- Toxoplasmosis
- Trimethadione
- Trisomy 8 mosaicism
- Tuberculosis
- Tularemia
- Tumor infiltration
- Typhoid fever
- Valganciclovir hydrochloride
- Varicella
- Vein compression syndrome
- Vinblastine
- Visceral leishmaniasis
- Vitamin b12 deficiency
- Yellow fever
- Zonisamide

# Contraindicated Medications
Leukopenia is considered an absolute contraindication to the use of the following medications:
- Methotrexate