Membrane Frizzled-related Protein Gene-related Ophthalmological Syndrome: 30-month Follow-up of a Sporadic Case and Review of Genotype-phenotype Correlation in the Literature

Purpose: To report a new sporadic case of membrane frizzled-related protein gene (MFRP)-related syndrome with a 30-month follow-up, and to review the literature for genotype-phenotype correlation in MFRP mutations.

Methods: A complete ophthalmological evaluation was performed at presentation and 30 months later, including best-corrected visual acuity test, slit lamp examination, fundoscopy, kinetic perimetry, electroretinography, fundus imaging (color, red-free, and autofluorescence), and morphologic-biometric analysis of the eye structures with an optical biometer, anterior-segment optical coherence tomography, retinal optical coherence tomography, and a confocal scanning laser for optic nerve head study. Polymerase chain reaction amplification of DNA obtained from peripheral blood lymphocytes and nucleotide sequencing of the complete MFRP gene were performed. The literature on cases of posterior microphthalmos and retinitis pigmentosa associated with MFRP mutations was reviewed.

Results: A 33-year-old female patient presented with posterior microphthalmos, retinitis pigmentosa with patches of retinal pigmented epithelium atrophy and scarce pigment mobilization, foveoschisis, and optic nerve drusen. After 30 months, progression of rod-cone retinal degeneration was detected. One obligate carrier showed a normal eye phenotype. A homozygote mutation in the MFRP gene (c.492delC), predicting a truncated protein (P166fsX190), was identified with genetic analysis. To our knowledge, 17 cases of MFRP-related syndrome have been reported in the literature, including the patient described herein. The phenotype of the syndrome, expressivity, and age of onset varied among and within the affected families. However, all patients sharing homozygous mutation c.492delC (alternatively named c.498delC) showed a complete phenotype (including foveoschisis and optic nerve head drusen), and similar fundus characteristics.

Conclusions: A new sporadic case of MFRP-related syndrome is reported. Review of the literature showed variability in the phenotype, but initial elements of genotype-phenotype correlation have been identified in patients sharing the mutation of the present case.