ZocdocAnswersWhat can cause low white blood cell count in a child?

Question

What can cause low white blood cell count in a child?

My 4 year old recently had a mild fever, cough which resulted in croup. Blood tests have returned with low white blood cell count and the doctor is ordering blood work again in a week. Is this something to worry about?

Answer

It is difficult to determine why your child would have a low white blood cell count, so it is important to speak with his pediatrician. My first question would be how low was the white blood cell count? White blood cell counts just below the lower limit of normal are sometimes normal or that person. For example, if your child had a white blood cell count of 3000, we might just consider this to be normal for your child even though it is below the lower limit of normal on some tests. The symptoms of mild fever, cough, and the diagnosis of croup really don't play a role in this finding. If your child was diagnosed with a bacterial infection, one would expect that the white blood cell count to be high and not low. Depending on his level, your pediatrician may decide just to recheck the blood of another time. It sounds like this is what your pediatricians doing. The more important question is what the differential of the white blood cell count is. The differential is the different types of white blood cells and whether or not the ratio of each are normal. One rare cause of low white blood cell count would be leukemia. This is likely what your pediatrician is attempting to rule out. Of note, most of the time leukemia causes a high white blood cell count. If you are particularly concerned about this, you could schedule an appointment with the pediatric hematologist.

This answer is for general informational purposes only and is not a substitute for professional medical advice.

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