A multiple congenital anomaly/mental retardation syndrome with a complex phenotype and age-related variability of expression. Typical facial appearance (elfin facies) is the most characteristic feature of this syndrome. Delayed growth, feeding difficulty, failure to thrive, colic, otitis media, and mental retardation are the early symptoms in infancy. Developmental disabilities and cardiovascular complications become apparent later in childhood. Hypertension, gastrointestinal problems, and genitourinary disorders usually complicate adult development. The phenotype may overlap with hypercalcemia with or without mental retardation and supravalvular aortic stenosis with or without mental retardation.