Cone pathway dysfunction in Jalili syndrome due to a novel familial variant of CNNM4 revealed by pupillometry and electrophysiologic investigations.

PURPOSE: To evaluate retinal function in a family presenting with Jalili syndrome due to a previously unreported variant in CNNM4.
METHODS: A family of three sisters with a novel CNNM4 variant, c.482 T > C p.(Leu161Pro), and ten visually normal, age-similar controls participated in this study. The subjects underwent detailed dental examinations and comprehensive ophthalmological examinations that included color vision testing, retinal imaging, and electroretinography. Full-field light- and dark-adapted luminance thresholds were obtained, in addition to light- and dark-adapted measures of the pupillary light reflex (PLR; pupil constriction elicited by a flash of light) across a range of stimulus luminance.
RESULTS: Clinical findings of cone dysfunction and amelogenesis imperfecta were observed, consistent with Jalili syndrome. Light-adapted ERGs were non-detectable in CNNM4 subjects, whereas dark-adapted ERGs were generally normal. Full-field luminance thresholds were normal under dark-adapted conditions and were elevated, but measurable, under light-adapted conditions. The CNNM4 subjects had large PLRs under dark-adapted conditions and responses near the lower limit of normal, or slightly subnormal, under light-adapted conditions.
CONCLUSION: CNNM4 variants can result in Jalili syndrome with cone dystrophy and generally preserved rod function. The PLR may be a useful measure for evaluating cone function in these individuals, as robust cone-mediated PLRs were recordable despite non-detectable light-adapted ERGs.