An error has been detected in the online mutation report by Burdon et al (J Med Genet 2004;41:e106). The mutation is identified in the manuscript as 226G>A in regards to the Genbank reference NM_021954. However, it should be 227G>A. The amino acid designation, R76H, is correct and this numbering error does not change any of the other results or conclusions of the article. The author apologises for this error.