Trisomy 18 mosaicism in an adult with normal intelligence.

A healthy 30-year-old woman was discovered unexpectedly to have trisomy 18/normal chromosome mosaicism. She was ascertained because of a history of three spontaneous abortions following the birth of a healthy son. Trisomy 18 was present in 18% of her lymphocytes and 2% of her cultured skin fibroblasts. She had several minor malformations associated with trisomy 18 syndrome. She is, to our knowledge, the first person who has clinical stigmata of trisomy 18 but has normal intelligence and leads a normal family life.