Choroideremia with Mutation in CHM Gene. Clinical Cases with Literature Review

The purpose: to describe clinical cases of choroideremia with mutation in CHM gene with molecular genetic verification of the diagnosis. Methods. Two relatives: a patient aged 33 and his mother’s sibs aged 39 with a rare hereditary retinal disease — choroideremia were examined. Patients’ full ophthalmic examination including autorefractometry, visual acuity testing with full correction, tonometry, biomicroscopy, fundus examination and photo as well as kinetic perimetry were performed. Electrophysiological examination included maximal electroretinogram (ERG), ERG to 30 Hz flicker and macular ERG (MERG) that were registered with electroretinograph MBN (Russia). Family anamnesis was studied. Genetic examination was performed for the verification of the diagnosis and pathologic gene molecular. Results. In 33-year-old patient advanced stage was diagnosed: best corrected visual acuity (BCVA) was OU 0,9, visual field was constricted to 10 degrees in both eyes. High BCVA and subnormal MERG correlated with comparatively preserved foveal structure on OCT. There was the terminal stage of choroideremia: In 39 years old his mother’s sibs BCVA was 0,1 OU, constricted to 5 degrees in both eyes. Maximal ERG and ERG to 30 Hz flicker were nonrecordable. Low BCVA and nonrecordable MERG correlated with defected retinal layers and cystoids macular edema on OCT. In both patients we revealed previously described pathogenic variant of nucleotic sequence in 6 exon of CHM gene (chrX:85213886 G>A), causing nonsense-mutation (p.Arg267*, NM_000390.2) in hemizygous state. Conclusion. Etiopathogenetic approach in choroideremia diagnostics allows providing correct diagnosis, prevention and developing of new treatment methods considering etiological factor.

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