Clinical feature and waveform in infantile nystagmus syndrome in children with FRMD7 gene mutations

Abstract

Infant nystagmus sydrome presents as involuntary eye movement disorder and can affect seriously ocular function. We performed a retrospective study of clinical data and FRMD7 genetic test results in 12 cases of infantile nystagmus syndrome to correlate waveform, stereopsis, and visual acuity. The patients (age 6.40±2.67 years) had FRMD7 mutations as follows: missense in eight cases, shear in two cases, frameshift in one case, and non-frameshift in one case. Horizontal jerk waveform was observed in six cases, versus horizontal pendulum in five cases and dual jerk in one case. The uncorrected visual acuity (24 eyes) was 0.21±0.12, compared with a corrected visual acuity (24 eyes) of 0.32±0.14. All patients had simultaneous perception, versus fusion function in 10 cases (83.33%) and stereoscopic vision in seven cases (58.33%) using the synoptophore. Eleven cases (91.67%) detected the stereo fly, compared with five cases (41.67%) for stereoscopic circles and seven cases (58.33%) for stereoscopic animals by Titmus test. Stereoscopic vision using the synoptophore did not correlate with the frequency, amplitude, or intensity of nystagmus or with corrected binocular visual acuity. The infantile nystagmus syndrome with FRMD7 mutations in our cases was caused primarily de novo and missense mutations. Visual acuity and binocular visual function were significant impaired, and the waveform was generally horizontal jerk. Also, an infrared videonystagmogram can record the frequency, amplitude, and intensity of nystagmus accurately.

X-linked FRMD7 gene mutation in idiopathic congenital nystagmus and its role in eye movement: A case report and literature review

“…The surgery balanced binocular vision and corrected the anomalous head posture at 3-year follow-up. The identified mutation caused substitution of CGC (that codes for Arg) with CTC (that codes for Leu) in eight exons of position of 229 in the FRMD7 gene, c.686G>T. Two other reports of missense mutation of the position 229 have been described in FRMD7 (17,18). One of them is a missense c.686C>G mutation in exon 8 of the FRMD7 gene, which results in the substitution of Gly(G) for Arg(R) at amino acid position 229 (p.R229G) (17).…”

“…One of them is a missense c.686C>G mutation in exon 8 of the FRMD7 gene, which results in the substitution of Gly(G) for Arg(R) at amino acid position 229 (p.R229G) ( 17 ). The other is a missense c.685C>T mutation, which causes the substitution of Arg (R) with Cys (C) at position 229 (p.R229C) in exon 8 of the FRMD7 gene ( 18 ). The missense mutations in position 229 of FRMD7 are mostly deleterious and attributed to the pathogenicity ( 18 ).The FRMD7 gene, located in chromosome Xq26.2, comprises 12 exons and encodes a polypeptide containing 714 residues ( 19 ).…”

“…The other is a missense c.685C>T mutation, which causes the substitution of Arg (R) with Cys (C) at position 229 (p.R229C) in exon 8 of the FRMD7 gene ( 18 ). The missense mutations in position 229 of FRMD7 are mostly deleterious and attributed to the pathogenicity ( 18 ).The FRMD7 gene, located in chromosome Xq26.2, comprises 12 exons and encodes a polypeptide containing 714 residues ( 19 ). The FRMD7 protein, containing FERM-N, FERM-M, FERM-C, and FA structural domains, is a member of the 4.1 superfamily ( 19 , 20 ).…”