Medical conditions Low white cell count may be due to acute viral infections, such as a cold or
influenza. It has been associated with
chemotherapy,
radiation therapy,
myelofibrosis,
aplastic anemia (failure of white cell, red cell and platelet production), stem cell transplant, bone marrow transplant,
HIV,
AIDS, and steroid use. Other causes of low white blood cell count include
systemic lupus erythematosus,
Hodgkin's lymphoma, some types of
cancer,
typhoid,
malaria,
tuberculosis,
dengue,
rickettsial infections, enlargement of the
spleen,
folate deficiencies,
psittacosis,
sepsis,
Sjögren syndrome and
Lyme disease. It has also been shown to be caused by deficiency in certain
minerals, such as
copper and
zinc. Pseudoleukopenia can develop upon the onset of infection. The leukocytes (primarily neutrophils, responding to injury first) start migrating toward the site of infection, where they can be scanned. Their migration causes bone marrow to produce more WBCs to combat infection as well as to restore the leukocytes in circulation, but as the blood sample is taken upon the onset of infection, it contains low amount of WBCs, which is why it is termed "pseudoleukopenia".
Medications Certain medications can alter the number and function of white blood cells. Medications that can cause leukopenia include
clozapine, an
antipsychotic medication with a rare adverse effect leading to the total absence of all granulocytes (neutrophils, basophils, eosinophils).
Minocycline, a commonly prescribed antibiotic, is another drug known to cause leukopenia. There are also reports of leukopenia caused by divalproex sodium or
valproic acid (Depakote), a drug used for epilepsy (seizures), mania (with bipolar disorder) and migraine. The
anticonvulsant drug,
lamotrigine, has been associated with a decrease in white blood cell count. The FDA monograph for
metronidazole states that this medication can also cause leukopenia, and the prescriber information suggests a complete blood count, including differential cell count, before and after, in particular, high-dose therapy.
Immunosuppressive drugs, such as
sirolimus,
mycophenolate mofetil,
tacrolimus,
ciclosporin,
leflunomide and
TNF inhibitors, have leukopenia as a known complication.
Interferons used to treat
multiple sclerosis, such as
interferon beta-1a and
interferon beta-1b, can also cause leukopenia.
Chemotherapy targets cells that grow rapidly, such as tumors, but can also affect white blood cells, because they are characterized by bone marrow as rapid growing. A common side effect of cancer treatment is
neutropenia, the lowering of
neutrophils (a specific type of white blood cell). Decreased white blood cell count may be present in cases of
arsenic toxicity. ==Diagnosis==