Posterior microphthalmos with retinal involvement related to MFRP gene: a report of 10 Brazilian patients

BACKGROUND

To describe the phenotype and genotype of 10 Brazilian patients with variants in MFRP, posterior microphthalmos and retinal findings.

METHODS

Complete ophthalmological evaluation was done at 4 different Brazilian centers. Genetic analysis was performed using commercial next generation sequencing panels for inherited retinal disorders.

RESULTS

Ages of the patients ranged from 10 to 65 years and visual acuities from 0,05 to no perception of light. All were hyperopes (+4,25 to + 17,50) with a short axial length (14,4 mm to 18 mm). Common posterior segment features, though not present in all, were optic disc drusen (5/10), foveoschisis (5/10) and retinal pigmentary changes (8/10). Isolated patients presented with macular atrophy, serous retinal detachment, and chorioretinal folds. The most common variant in MFRP found in our patients was a deletion in exon 5 (c.498delC; p.Asn267Thrfs *25), present in all except 2 patients. Other variants found were c.523C>T (p.Gln175*), c.298delG (p.Ala100Argfs *37), c.666del (p.Thr223Argfs *83) and the novel variant c.257C>A (p.Ala86Asp).

CONCLUSIONS

This is the first report of Brazilian patients with posterior microphthalmos and pathogenic variants in MFRP and the first describe of the variant p.Ala86Asp in literature. Our cases confirm the previously reported phenotype of high hyperopia, optic disc drusen, alterations in foveal architecture, retinal pigmentary changes with loss of photoreceptor function and visual field constriction. Report of such a rare condition is important to increase awareness to the phenotype of posterior microphthalmia with associated retinal conditions.

Molecular and Clinical Characterization of CNGA3 and CNGB3 Genes in Brazilian Patients Affected with Achromatopsia

Achromatopsia (ACHM) is a congenital cone photoreceptor disorder characterized by reduced visual acuity, nystagmus, photophobia, and very poor or absent color vision. Pathogenic variants in six genes encoding proteins composing the cone phototransduction cascade (CNGA3, CNGB3, PDE6C, PDE6H, GNAT2) and of the unfolded protein response (ATF6) have been related to ACHM cases, while CNGA3 and CNGB3 alone are responsible for most cases. Herein, we provide a clinical and molecular overview of 42 Brazilian patients from 38 families affected with ACHM related to biallelic pathogenic variants in the CNGA3 and CNGB3 genes. Patients' genotype and phenotype were retrospectively evaluated. The majority of CNGA3 variants were missense, and the most prevalent CNGB3 variant was c.1148delC (p.Thr383Ilefs*13), resulting in a frameshift and premature stop codon, which is compatible with previous publications in the literature. A novel variant c.1893T>A (p.Tyr631*) in the CNGB3 gene is reported for the first time in this study. A great variability in morphologic findings was observed in our patients, although no consistent correlation with age and disease stage in OCT foveal morphology was found. The better understanding of the genetic variants landscape in the Brazilian population will help in the diagnosis of this disease.

Macular dystrophies associated with Stargardt-like phenotypes

PURPOSE

Stargardt-like phenotype has been described as associated with pathogenic variants besides the ABCA4 gene. This study aimed to describe four cases with retinal appearance of Stargardt disease phenotypes and unexpected molecular findings.

METHODS

This report reviewed medical records of four patients with macular dystrophy and clinical features of Stargardt disease. Ophthalmic examination, fundus imaging, and next-generation sequencing were performed to evaluate pathogenic variants related to the phenotypes.

RESULTS

Patients presented macular atrophy and pigmentary changes suggesting Stargardt disease. The phenotypes of the two patients were associated with autosomal dominant inheritance pattern genes (RIMS1 and CRX) and in the other two patients were associated with recessive dominant inheritance pattern genes (CRB1 and RDH12) with variants predicted to be pathogenic.

CONCLUSION

Macular dystrophies may have phenotypic similarities to Stargardt-like phenotype associated with other genes besides the classic ones.