Treatment and assessment is always done of people and not numbers, so this list of causes may seem intimidating and offputting as I do not know your son or what his symptoms are.
Monocytes and Basophils are a type of white blood cells. It is the white blood cells that protect and defend the body against germs and bacteria.
There are different types of white blood cells, and each type of white blood cell does a specific task. Your sons blood test tested for each specific type, and that number is XXXXX as a percentage of the whole total of white blood cells.
It will help you understand if I explain all, so I shall. NEUT stands for Neutrophils, and they specialize in fighting off bacterial infections. Your sons levels were normal.LYMPH stands for lymphocytes, which specialize in fighting viral infections. Again, your sons were normal. BASO stands for basophils which specialize in fighting parasitic infections Your sons were high, which will be explained. EO stands for eosinophils, and they specialize in allergic responses. Again, your sons were normal. MONOCYTES (MONO) specialize in severe infections.
Elevated MONOCYTES have many reasons...the most common causes are bacterial infections. Several types of cancer as well can cause an increase in monocytes, as can chronic ulcerative collitis, collagen disease, and some parasitic disorders.
Elevated BASOPHILS are found in some kinds of cancers, especially leukemia, hodgekins disease. It also occurs in inflammation, sinusitis, can occur in blood disorders such as anemia and polycythemia vera, and in some infections like chickenpox and the flu.
I hope I was able to help, and if I can clarify further, please let me know.