Abstract
Purpose:
To define the retinal histopathology in donor eyes from a patient with a cone dystrophy of unknown genetic origin.
Methods:
Eyes were obtained from a 54 year-old female and were fixed within 13 hours postmortem. Globes were evaluated with macroscopic, SLO and OCT imaging. Perifoveal and peripheral regions were processed for electron microscopy and immunocytochemistry using cell-specific antibodies. Two age-matched normal eyes were used as controls. DNA was obtained from a blood sample of the donor and analyzed for 26 cone dystrophy genes by next generation sequencing at a CLIA lab.
Results:
Fundus macroscopy and SLO showed an abnormal ring encompassing most of the macula and centered on the fovea. OCT showed retinal thinning in this region. Histology confirmed the presence of this lesion, which measured ~5.5mm in diameter. There was an abrupt transition at the periphery of the lesion. Outside the lesion several rows of nuclei were present in the ONL, but within the lesion, only occasional patches of stubby cones projected from the outer limiting membrane. The far periphery was characterized by the presence of cystoid degeneration as evidenced by cyst-like luminal spaces in the inner and outer plexiform layer. Immunocytochemistry revealed patches of cone arrestin labeled cells in the lesion but this labeling was reduced in the periphery. Co-labeling with cone opsin antibodies was not observed in these cells. Rhodopsin-positive cells were rarely observed in the central lesion, but were prominent throughout the rest of the retina. DNA analysis failed to identify a mutation in any of the genes analyzed (ABCA4, ADAM9, AIPL1, BEST1, c8ORF37, CACNA1F, CACNA2D4, CDHR1, CERKL, CNGB3, CNNM4, CRX, GUCA1A, GUCY2D, KCNV2, PDE6C, PDE6H, PITPNM3, PROM1, PRPH2/RDS, RAX2, RDH5, RIMS1, RPGRIP1, SEMA4A, and UNC119). As additional cone dystrophy genes are discovered, further mutation testing will be performed.
Conclusions:
The histopathology of the retina in a patient with a cone dystrophy of unknown genetic etiology displayed a central lesion characterized by degenerated cones and the absence of rod photoreceptors.