Low White Blood Cell Count

I have a brother that is 47 years old and has Downs Syndrome.  He is on many medications including synthroid, depakote, mellaril, seroquil, atavan and ambien.  Not sure if that is all of them.  He is also in mild renal failure showing low potassium levels.  He has a WBC of 2.8 and his kidney dr. is referring him to an Oncologist suspecting that there may be a bone marrow problem ie: leukemia?  Can anyone give me more info on what this WBC can represent and what else they may need to test for?  Could it be a B12 or thyroid issue?  How serious is this low level?  Referring him to an Oncologist has me worried.  Thanks in advance !  Suzanne

[emtd65]

Answer
Sometimes the cause of a low white blood cell count can't be determined (idiopathic). Known causes of a low white blood cell count (leukopenia) include:

Infections, such as viral infections and HIV
Autoimmune disorders, such as lupus
Certain medications, especially those used in chemotherapy and some antibiotics
Radiation therapy
Bone marrow disease, such as leukemia or myelodysplastic syndromes
White blood cells help fight infection in your body. A normal white blood cell count ranges from 4,500 to 10,000 cells per microliter of blood. A mild decrease in white blood cells below 4,500 cells per microliter doesn't necessarily indicate a serious illness. However, a dangerously low white blood cell count — below 2,500 cells per microliter — increases the risk of serious infection


Hope this helps - it is from The Mayo Clinic site

Christine