Abstract
Purpose::
To define the morphology and distribution of photoreceptor markers in a donor eye from a female symptomatic carrier of choroideremia donor with an X linked choroideremia. This donor was a member of a family in which multiple female carriers have macular dysfunction.
Methods::
A multi-generation family with X-linked choroideremia was evaluated over two decades with dilated fundus examination, photography, visual field testing and electroretinography. A family history was obtained, and molecular testing was performed. The donor died at age 91 and eyes were fixed in 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer. Paraffin tissue sections from 3 different areas of the eye were studied by indirect immunofluorescence, using well-characterized monoclonal antibodies to the cone and rod specific markers. Also, representative samples were processed for electron microscopy analysis.
Results::
At age 77, fundus examination revealed a reticular pigmentary retinopathy throughout the mid and far periphery; the ERG was normal. Within 10 years, she developed night blindness and significant central vision impairment. Molecular testing in the family revealed the heterozygous splice site mutation 1413+1 G>A in CHM. Postmortem morphological analysis of the donor revealed RPE thinning and pigment clumping typical for choroideremia, as well as photoreceptor degeneration in some areas and basal laminar deposits. In addition, a great number of drusen was observed in the donor's fovea. Labeling of the sections with the cone cytoplasmic marker revealed no differences when compared to the control eye. However, labeling with cone opsin antibodies revealed that cones were drastically affected. Blue opsin was almost completely absent in the affected retina. Moreover, red/green opsins were distributed along the entire plasma membrane of cones with this pigment type in all observed areas. Also, rhodopsin was also distributed along the entire rod plasma membrane in all the observed areas.
Conclusions::
Morphological changes typical of choroideremia were observed in the RPE and photoreceptors of the carrier donor. However, the histological data obtained suggests that the clinical manifestation of this donor seems to be related to abnormal distribution of both cone opsins and rhodopsin.
Keywords: retinal degenerations: cell biology • immunohistochemistry • photoreceptors