Two siblings with late-onset cone-rod dystrophy and no visible macular degeneration

Occult Macular Dysfunction Syndrome: Identification of Multiple Pathologies in a Clinical Spectrum of Macular Dysfunction with Normal Fundus in East Asian Patients: EAOMD Report No. 5

Occult macular dystrophy (OMD) is the most prevalent form of macular dystrophy in East Asia. Beyond RP1L1, causative genes and mechanisms remain largely uncharacterised. This study aimed to delineate the clinical and genetic characteristics of OMD syndrome (OMDS). Patients clinically diagnosed with OMDS in Japan, South Korea, and China were enrolled. The inclusion criteria were as follows: (1) macular dysfunction and (2) normal fundus appearance. Comprehensive clinical evaluation and genetic assessment were performed to identify the disease-causing variants. Clinical parameters were compared among the genotype groups. Seventy-two patients with OMDS from fifty families were included. The causative genes were RP1L1 in forty-seven patients from thirty families (30/50, 60.0%), CRX in two patients from one family (1/50, 2.0%), GUCY2D in two patients from two families (2/50, 4.0%), and no genes were identified in twenty-one patients from seventeen families (17/50, 34.0%). Different severities were observed in terms of disease onset and the prognosis of visual acuity reduction. This multicentre large cohort study furthers our understanding of the phenotypic and genotypic spectra of patients with macular dystrophy and normal fundus. Evidently, OMDS encompasses multiple Mendelian retinal disorders, each representing unique pathologies that dictate their respective severity and prognostic patterns.

Novel compound heterozygous mutation in the POC1B gene underlie peripheral cone dystrophy in a Chinese family

PURPOSE

To describe the clinical characteristics of a Chinese family with peripheral cone dystrophy (PCD) and identify the gene mutations causing PCD.

METHODS

The Chinese PCD pedigree underwent comprehensive ophthalmic examinations, including visual acuity, slit lamp examination, fundoscopy, visual field examination, autofluorescence, fluorescence fundus angiography and indocyanine green angiography, full-field electroretinograms, and spectral-domain optical coherence tomography. The targeted next-generation sequencing of COD or cone-rod dystrophy (CORD) genes was used to identify the causative mutation.

RESULT

The fundus characteristics of the Chinese patient were consistent with PCD. The novel compound heterozygous mutation, c.1354C>T and c.710A>G, in POC1B was identified in the patient, the mutations were segregated with the PCD phenotype in the family and were absent from ethnically matched control chromosomes. Prediction analysis demonstrated the novel missense mutation, POC1B c.710A>G, might be damaging.

CONCLUSIONS

PCD was a type of COD or CORD and the novel compound heterozygous mutation in POC1B was responsible for PCD phenotype in the family.