TWIN ZYGOSITY TESTING FOR MEDICAL PURPOSES

After being poisoned by eating the mushroom species Cortinarius specio sissimus, a twin developed interstitial nephritis with acute renal fai lure, He received a renal transplant from his living twin brother, who was presumed dizygotic on phenotypic grounds. Fifteen years later, th e twins were zygosity tested by DNA ''fingerprint analysis'' and found to be monozygotic, despite important phenotypic discordances. The rec ipient has discontinued immunosuppression therapy and remains well aft er 9 months. We suggest that, for medical and other reasons, zygosity should be determined at birth on all like-sexed twins. (C) 1998 Wiley- Liss, Inc.