The importance of establishing a genetic diagnosis in patients with a choroideremia phenotype has been underscored by the advent of gene replacement therapy for this condition. Here, we describe a complex imbalance at the CHM locus in a male patient with classical disease. At the DNA level, this imbalance consists of 2 non-contiguous duplications (exons 1-2 and 9-12). Further characterization suggests the generation of 2 independent CHM transcriptional units, one of which may produce a deleted form of the Rab escort protein 1 protein. Expression of such a type of aberrant protein in photoreceptors may have important implications when considering gene therapy for this disorder.
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choroideremia, copy number variation, genetic testing, ophthalmology, retinal dystrophy, structural variation