The Costello syndrome is characterized by dwarfism, unique cutaneous l
esions, distinct facial gestalt, and mental retardation. We present a
Japanese patient with the Costello syndrome. She showed high serum IgM
level during the early infantile period. Nissen's fundplication was c
arried out to treat severe gastroesophageal reflux. Endocrinological i
nvestigations revealed a partial deficiency of growth hormone.