The Costello syndrome is characterized by dwarfism, unique cutaneous lesions, 
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 carried out to treat severe 
gastroesophageal reflux. Endocrinological investigations revealed a partial 
deficiency of growth hormone.