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

• Published in: Japanese journal of ophthalmology 2017, Vol.61 (1), p.92-98
• Main Authors: Ueno, Shinji, Nakanishi, Ayami, Kominami, Taro, Ito, Yasuki, Hayashi, Takaaki, Yoshitake, Kazutoshi, Kawamura, Yuichi, Tsunoda, Kazushige, Iwata, Takeshi, Terasaki, Hiroko
• Format: Article
• Language: English
• Subjects: Adolescent; Clinical Investigation; Color Vision Defects - diagnosis; Color Vision Defects - genetics; Color Vision Defects - metabolism; Electroretinography; Eye Proteins - genetics; Eye Proteins - metabolism; Fluorescein Angiography; Fundus Oculi; Genetic Variation; Humans; Male; Medicine; Medicine & Public Health; Ophthalmology; Retinal Cone Photoreceptor Cells - cytology; Visual Acuity; Visual Field Tests
• ISSN: 0021-5155; 1613-2246
• DOI: 10.1007/s10384-016-0484-7

Purpose 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. Patient and methods 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. Results 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. Conclusions 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.