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Array comparative genomic hybridisation– first line genetic investigation for learning disability, developmental delay or intractable seizures?

We would like to highlight the role of microarray based comparative genomic hybridisation (array CGH) in the diagnostic work up of children with learning disability, developmental delay or intractable seizures. We present two cases in which the diagnosis was made based on array CGH when previous investigations were negative. Case 1 Potocki Lupski Syndrome (PTLS or duplication of chromosome 17p11.2) A Caucasian boy presented with developmental delay and feeding difficulties in early childhood, with no significant dysmorphism or other clinical features. Investigations including karyotyping were negative. Re-evaluation by the Geneticist at 10 years of age led to the diagnosis of PTLS from array CGH test. The genetic association of PTLS to Charcot Marie Tooth disease (CMT) was noted and may have implication on patients diagnosed with CMT. Case 2 Wolf–Hirschhorn syndrome (WHS or microdeletion of 4p 16.3) with trisomy of terminal region of 19q. An Asian boy born to consanguineous parents, who was small for date, had cystic dysplasia of kidneys and dysmorphic features presented with intractable seizures from 5 months of age. Karyotyping and other extensive investigations undertaken did not reveal the aetiology. However array CGH led to the diagnosis of WFS with trisomy of terminal 19q at 18 months of age. Conclusions Earlier use of array CGH could have prevented diagnostic delay in the two cases. The higher cost over karyotyping can be justified by the number of tests and the diagnostic dilemma that could potentially be avoided. The advantages of array CGH makes it the first line genetic investigation of choice in learning disability, developmental delay and in intractable seizures. There is potential for identification of genetically related conditions as in the case of PTLS and CMT. It is important to publicise the advantages of array CGH among clinicians and the Commissioners in order to make the test more freely available throughout the UK.