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Caterina Toma, Giulio Ruberto, Enza Maria Valente, Sabrina Signorini, Chiara Bertone, Mauro Antonini, Paolo Emilio Bianchi; FUNCTIONAL AND GENETIC FINDINGS IN PATIENTS AFFECTED BY JOUBERT SYNDROME: RETINAL DYSTROPHY IS CONNECTED WITH DEFINITE CAUSATIVE GENES. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5865.
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Joubert syndrome (JS) is a rare autosomal recessive or X-linked non-progressive congenital ataxia, characterized by a peculiar malformation of the brainstem and cerebellar vermis. Over 30 genes are known to cause JS, all involved in the structure or functioning of the primary cilium. Visual system anomalies and oculomotor system defects are relatively frequent in JS, especially in association with specific gene defects, such as AHI1 and CEP290. Aim of the present study was to assess the ability of electroretinography (ERG) and patterned visual evoked potentials (pVEP) to detect functional retinal and visual pathway anomalies in JS patients with or without retinal dystrophy.
In this retrospective study, 44 patients who met diagnostic criteria for JS were included. Every patient underwent a complete neuro-ophthalmological evaluation as well as repeated ERG and pVEP recordings. Genetic testing was performed in 40 patients by means of a next-generation-sequencing based targeted resequencing of 120 ciliopathy-related genes, including all known JS genes. We compared quantitative and qualitative data of patients with (n=25) and without (n=19) retinal dystrophy, and attempted to correlate ophthalmologic data with genetic results. A control ERG and pVEP normative group present in our database was compared with the JS patients.
There was a significant difference in the ERG and pVEP recordings between patients with retinal dystrophy and patients without retinal dystrophy. The analysis for repeated ERG and pVEP measures demonstrated a reduction in the “a” and “b” waves amplitudes and in pVEP amplitudes in JS retinal dystrophic subjects respect the non dystrophic. Pathogenic biallelic mutations in a known JS gene were identified in 30 (75%) pts, including 12 out of 22 (55%) without and all 18 patients (100%) with retinal dystrophy. Interestingly, we did not find any genetic overlap among the two groups: retinal dystrophy was associated to mutations in AHI1, CEP290, INPP5E, OFD1 and TMEM67, while patients without retinal dystrophy carried mutations in C5Orf42, CC2D2A, RPGRIP1L, KIF7, NPHP1, TCTN1 and TMEM237 genes.
ERG and pVEP provide useful functional information about retinal involvement characteristics and visual pathways in subjects affected by Joubert syndrome.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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