1. ¹Institute of Medical Genetics, Catholic University, Rome, Italy
2. ²JC Self Research Institute of Human Genetics, Greenwood Genetic Center, Greenwood, SC, USA
3. ³Department of Genetic Medicine, Women's and Children's Hospital, Adelaide, South Australia, Australia
4. ⁴Department of Paediatrics, University of Adelaide, Adelaide, South Australia, Australia

Correspondence: Professor P Chiurazzi and Professor G Neri, Institute of Medical Genetics, Catholic University, Largo F. Vito 1, Rome 00168, Italy. Tel: +39 06 3054449; Fax: +39 06 3050031; E-mails: pietro.chiurazzi@rm.unicatt.it and gneri@rm.unicatt.it

Received 25 August 2007; Revised 28 November 2007; Accepted 5 December 2007; Published online 16 January 2008.

Abstract

X-linked mental retardation (XLMR) is a common cause of inherited intellectual disability with an estimated prevalence of 1/1000 males. Most XLMR conditions are inherited as X-linked recessive traits, although female carriers may manifest usually milder symptoms. We have listed 215 XLMR conditions, subdivided according to their clinical presentation: 149 with specific clinical findings, including 98 syndromes and 51 neuromuscular conditions, and 66 nonspecific (MRX) forms. We also present a map of the 82 XLMR genes cloned to date (November 2007) and a map of the 97 conditions that have been positioned by linkage analysis or cytogenetic breakpoints. We briefly consider the molecular function of known XLMR proteins and discuss the possible strategies to identify the remaining XLMR genes. Final remarks are made on the natural history of XLMR conditions and on diagnostic issues.