Prion diseases and iatrogenic infections I. A review.

Iatrogenic diseases are disorders caused by the treatment of physician or surgeon (iatros from Greek "healer"). The disease develops by transmission of prion-infected material from the (clinically inapparent) donor to the recipient. First case significantly confirmed by animal bioassay was described in a corneal transplant 1974 and another following a neurosurgical procedure in 1977. Over one hundred of cases were detected in recipients of cadaveric, prion infected pituitary hormones (mostly growth hormone or, significantly less, gonadotrophins); the majority in France, UK and USA. Over one hundred of cases were detected following transplantation of prion-infected dura mater (mostly lyophilized commercial preparations) mostly in Japan. Some hormonal as well dura mater cases still occur because of an enormously prolonged incubation period. There are no fresh cases because cadaveric hormones were replaced by synthetic preparations and cadaveric dura mater by autologous tissue (fascia lata, fascia temporalis). Actual problems of iatrogenic prion infections are confined to surgery/neurosurgery, ophthalmology, otorhinolaryngology and dental surgery. Prions have also been detected outside the central nervous system, posterior eye, peripheral nerves, muscles, spleen, lymphoreticular system as tonsils and appendix, intestine, urine (?), olfactory cilia and central olfactory pathway representing a route of infection (nasal secretions). General anaesthesia may also be involved. Medical devices in contact with infected tissues became contaminated within minutes. Iatrogenic infections may occur thereafter incubating for years or decades. They are difficult to register because the hospital documentation has been actually kept for ten years only. It is evident that prion diseases have frequently a surgical history, according to some authors in one third of patients. Another problem of greatest importance is the prion decontamination of infected medical devices that is really difficult at present and rarely, if ever, properly performed in greatest majority of world hospitals. The decontamination methods will be presented in the second part of this article.