Ciliopathies are an expanding group of rare conditions characterised by multiorgan involvement, that are caused by mutations in genes encoding for proteins of the primary cilium or its apparatus. Among these genes, CEP290 bears an intriguing allelic spectrum, being commonly mutated in Joubert syndrome and related disorders (JSRD), Meckel syndrome (MKS), Senior-Loken syndrome and isolated Leber congenital amaurosis (LCA). Although these conditions are recessively inherited, in a subset of patients only one CEP290 mutation could be detected.
To assess whether genomic rearrangements involving the CEP290 gene could represent a possible mutational mechanism in these cases, exon dosage analysis on genomic DNA was performed in two groups of CEP290 heterozygous patients, including five JSRD/MKS cases and four LCA, respectively. In one JSRD patient, we identified a large heterozygous deletion encompassing CEP290 C-terminus, that resulted in marked reduction of mRNA expression. No copy number alterations were identified in the remaining probands.
The present work expands the CEP290 genotypic spectrum to include multiexon deletions. Although this mechanism does not appear to be frequent, screening for genomic rearrangements should be considered in patients in whom a single CEP290 mutated allele was identified.
A child developed minor motor seizures at the age of 14 months accompanied by an abnormal electroencephalogram showing single spikes and polyspikes over the vertex and frontocentral regions. Seizures continued until the age of 22 months despite administration of several standard anticonvulsants. At age 22 months, pyridoxine, 75 mg daily, was initiated and anticonvulsants were discontinued. Both the seizures and the electroencephalographic abnormality have disappeared over the ensuing 20 months with pyridoxine therapy.
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