1. A case of ocular cystinosis associated with two potentially severeCTNSmutations
- Author
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John A. Sayer, Francisco C. Figueiredo, Gustavo S. Figueiredo, Andrew C Browning, Clare E. Beesley, Emma Montgomery, Oliver Baylis, and Elisa Molinari
- Subjects
Adult ,0301 basic medicine ,Proband ,Heterozygote ,RNA Splicing ,Cystinosis ,030105 genetics & heredity ,Gene mutation ,Real-Time Polymerase Chain Reaction ,Slit Lamp Microscopy ,medicine.disease_cause ,Compound heterozygosity ,Conjunctival Diseases ,Corneal Diseases ,03 medical and health sciences ,Exon ,0302 clinical medicine ,Microscopy, Electron, Transmission ,medicine ,Humans ,Genetic Association Studies ,Genetics (clinical) ,Mutation ,Microscopy, Confocal ,business.industry ,Intron ,Sequence Analysis, DNA ,medicine.disease ,Molecular biology ,eye diseases ,Pedigree ,Ophthalmology ,Amino Acid Transport Systems, Neutral ,Cystinosin ,Pediatrics, Perinatology and Child Health ,030221 ophthalmology & optometry ,Female ,sense organs ,business - Abstract
Background Ocular cystinosis is a rare autosomal recessive disorder caused by one severe and one mild mutation in the CTNS gene. It is characterised by cystine deposition within the cornea and conjunctiva however, the kidneys are not affected. We report a case of ocular cystinosis caused by two potentially severe CTNS mutations and discuss the possible mechanism of renal sparing. Methods This is an observational case report of the proband and her unaffected relatives. All subjects underwent ophthalmic examination, whilst in the proband, In vivo laser scanning confocal microscopy was used to demonstrate cystine crystals within her corneas and conjunctiva. Genetic diagnosis was confirmed by DNA sequencing of the proband and the segregation of the mutations was established in her relatives. RT-PCR of leukocyte RNA was undertaken to determine if aberrant splicing of the CTNS gene was taking place Results: The proband was found to have cystine crystals limited to the anterior corneal stroma and the conjunctiva. Sequencing of the proband's CTNS gene found her to be a compound heterozygote for a 27bp deletion in exon8/intron 8 (c.559_561 + 24del) and a novel c.635C>T variant in exon 9 that is predicted be pathogenic and to result in the substitution of alanine with valine at amino acid position 212 (p.Ala212Val), which is within the 3rd transmembrane spanning domain of the CTNS protein. Examination of the proband's leukocyte RNA failed to demonstrate any aberrant CTNS gene splicing. Conclusion We present a case of ocular cystinosis caused by two potentially severe CTNS gene mutations. The lack of renal involvement may be due to localised (ocular) aberrant CTNS RNA splicing.
- Published
- 2019
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