CD4 and chronic obstructive pulmonary disease: The mechanism for CD4 T lymphocyte decline without lymphopenia in this patient was unclear, the preceding exposure to high dose dexamethasone might have been an important contributing factor, since corticosteroids can reduce CD4 T lymphocytes numbers and inhibit their functions [1,2,10], thus an important risk factor for colonization of Pneumocystis jiroveci in patients with chronic obstructive pulmonary disease or lung cancer [8].