We describe a mentally retarded 12-year-old girl with ataxia in whom diagnostic evaluation for short stature revealed isolated growth hormone (GH) deficiency and multiple central nervous system (CNS) lesions. Assessment of immunologic status, performed because of the persistence of recurrent respiratory tract infections, showed associated deficiencies of IgG2-IgG4 and specific antibody response; in addition, in vitro lymphocyte response to mitogens was low, in vitro production of interleukin-2 and of IgM was absent, and natural killer activity was decreased. The possibility that association of the CNS lesions, GH deficiency and immune defects could be due to alterations of the neuro-immuno-endocrine network secondary to a disturbance of neurotransmitters induced by precocious CNS damage of a viral or ischemic nature is discussed.