Growth hormone deficiency (GHD) may be associated with a number of immunodeficiency diseases, but its association with immunoglobulin class switch recombination (Ig CSR) deficiencies is very rare. We report the case of a patient with a history of recurrent diarrhea and respiratory infections diagnosed with hyper IgM syndrome on the basis of immunological findings (low serum levels of IgG and IgA and an elevated serum level of IgM). In view of the patient's short stature, growth hormone evaluation was performed and growth hormone deficiency confirmed. The patient received growth hormone therapy in addition to Ig replacement therapy and antibiotics and responded well. As the coding regions of the genes known to be responsible for Ig CSR (CD40L, CD40, AICDA, and UNG) were intact in our patient, this might be a new form of Ig CSR deficiency.