Genetic analysis of a family with posterior segment microphthalmia-retinoschisis and drusen syndrome

Objective  To analyze the clinical phenotypes and genotypes of a family with posterior segment microphthalmia-retinoschisis and drusen syndrome.

Methods  A pedigree investigation study was conducted.A family with four members across two generations treated at Shenzhen Eye Hospital in July 2021 was enrolled.Detailed ophthalmic examinations, including best corrected visual acuity (BCVA), intraocular pressure, slit-lamp microscopy, color fundus photography, optical coherence tomography (OCT), anterior segment OCT, fundus fluorescein angiography (FFA), and visual field tests were performed in the four members.Peripheral venous blood samples were collected from members for whole exome sequencing and data analysis.The pathogenicity of novel variant sites was assessed according to the ACMG guidelines.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Shenzhen Eye Hospital (No.22KYPJ018).Written informed consent was obtained from each subject or the guardian.

Results  The proband is a 14-year-old female with high hyperopia since childhood, BCVA of + 9.75 DS-0.75 DC×150°=0.9 and + 11.75 DS-1.25 DC×30°=0.7, corneal transverse diameters of 12.1 and 12.2 mm, anterior chamber depths of 2.56 and 2.92 mm, lens thicknesses of 3.92 and 3.94 mm, and axial lengths of 17.47 and 17.01 mm in the right and left eyes, respectively.Fundus photography revealed diffuse yellow-white drusen-like lesions with unclear borders in the mid-peripheral retina, while OCT showed retinoschisis in the inner nuclear layer and homogeneous mound-like elevations with hyperreflective dense spots under the retinal pigment epithelium.FFA demonstrated diffuse punctate transilllumination of the mid-peripheral retina in both eyes, and visual field tests revealed a general decrease in visual acuity.The proband’s 8-year-old brother exhibited similar signs to the proband.The consanguineously married parents were phenotypically normal.Whole exome sequencing identified compound heterozygous mutations in the membrane frizzled-related protein ( MFRP) gene in the proband and her brother, c.1150_1151insC (p.His384Profs*8) in exon 5 and c. 498_499insC (p.Asn167Glnfs*34) in exon 10.The father carried the c. 498_499insC mutation, while the mother carried the c.1150_1151insC mutation.Both were frameshift mutations predicted to alter gene function.These novel mutations had not been reported in the ESP, 1 000 Genomes (Phase 3), or ExAC databases, indicating they are novel variants.The variants co-segregated with the disease and both were classified as pathogenic according to ACMG guidelines.Based on the clinical and genetic findings, the family was diagnosed with posterior segment microphthalmia-retinoschisis and drusen syndrome, inherited in an autosomal recessive manner.

Conclusions  The MFRP gene mutations c. 1150_1151insC and c. 498_499insC are the pathogenic variants for the posterior segment microphthalmia-retinoschisis and drusen syndrome in this family, and these compound heterozygous mutations are reported for the first time.

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