We read with great interest the article by Schwarzbraun et al on predictive diagnosis of Li–Fraumeni syndrome established as an accidental finding in whole genome array testing, originally performed to identify the molecular cause of mental retardation (MR) in a 7-year-old child.1 We would like to expand the spectrum of unexpected and unintended findings with this new technique. In a 5-year-old Kurdish boy with MR and normal karyotype, array comparative genomic hybridisation (CGH) with an Agilent platform (using the Human Genome CGH 244A Microarray Kit with a medium spatial resolution of 12 kb and a threshold of five consecutive aberrant clones) identified a heterozygous intragenic deletion spanning exons 4 and 5 of the Parkin gene (PARK2) as the only significant change (minimal deletion boundaries for NCBI Build 36, chromosome 6: 162,339,755–162,582,128). Bi-allelic mutations of Parkin cause early onset parkinsonism (OMIM 600116), a neurodegenerative disorder without phenotypic overlap to the MR syndrome of the 5-year-old boy. Hence, array CGH accidentally revealed a carrier status for a more late onset autosomal recessive disease.

We informed the patient’s parents about this result. They planned to have another child and asked us about the risk for their future offspring being affected by this type of parkinsonism. The maximum frequency of putative recessive heterozygous Parkin mutations reported in the literature …