In vivo imaging of a cone mosaic in a patient with achromatopsia associated with a GNAT2 variant.

The 2 most common causative genes for achromatopsia (ACHM) are CNGA3 and CNGB3; other genes including GNAT2 account for only a small portion of ACHM cases. The cone mosaics in eyes with CNGA3 and CNGB3 variants are severely disrupted; the cone mosaics in patients with GNAT2-associated ACHM; however, have been reported to show a contiguous pattern in adaptive optics (AO) retinal images. The purpose of this study was to analyze the cone mosaic of another case of GNAT2-associated ACHM. The patient was a 17-year-old Japanese boy. Comprehensive ocular examinations including fundus photography, electroretinography (ERGs), optical coherence tomography (OCT), and whole-exome analysis were performed. The cone mosaic was recorded with a flood-illuminated AO fundus camera, and the cone density was compared with those of 10 normal control eyes. The patient had the typical phenotype of ACHM, and a novel homozygous variant, c.730_743del, in GNAT2 was identified. The fundus did not show any specific abnormalities, and the OCT images showed the presence of the ellipsoid zone. The AO fundus image showed a clearly defined cone mosaic around the fovea. The cone density at 500 μm from the fovea was reduced by 15-30 % as compared with those of the normal eyes. This is the first description of a Japanese patient with ACHM with a novel GNAT2 variant. The eyes of this patient had a preserved cone structure with loss of function.

Citation

Shinji Ueno, Ayami Nakanishi, Taro Kominami, Yasuki Ito, Takaaki Hayashi, Kazutoshi Yoshitake, Yuichi Kawamura, Kazushige Tsunoda, Takeshi Iwata, Hiroko Terasaki. In vivo imaging of a cone mosaic in a patient with achromatopsia associated with a GNAT2 variant. Japanese journal of ophthalmology. 2017 Jan;61(1):92-98

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PMID: 27718025

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