Phenotypic characterization of a Chinese family with autosomal dominant cone-rod dystrophy related to GUCY2D.

BACKGROUND

This study aimed to evaluate the clinical phenotype and investigate the molecular genetic defect in a Chinese family with autosomal dominant cone-rod dystrophy (ADCRD).

METHODS

Family history was collected and patients underwent regular ophthalmologic examinations. Two affected individuals underwent three-year follow-ups to analyze the course of the disease. Venous blood was collected from family members and genomic DNA was extracted. A whole genome linkage analysis of 11 family members was performed using an Illumina Infinium Human Linkage-12 panel. All exons and exon-intron boundaries of guanylate cyclase 2D gene (GUCY2D) were sequenced for familial gene mutation.

RESULTS

Decreased visual acuity and photophobia usually commenced in early childhood in these patients. The family demonstrated an age-dependent increase in macular abnormalities with progressive development of geographic atrophy. Electrophysiological testing revealed a marked loss of cone function. Initially, a genome-wide linkage analysis mapped the disease to chromosome 17 (1-36 cM), with a maximum LOD score of 1.505. Sequence analysis of the GUCY2D gene in the linkage interval detected a recurrent heterozygous mutation, c.2513G > C (p.R838P). This mutation appeared in all seven patients with ADCRD but did not appear in any of the four unaffected family members.

CONCLUSIONS

A missense mutation in the GUCY2D gene caused ADCRD in this family. Clinical follow-up of this family with a typical CRD phenotype revealed disease progression during the time period.