Clinical characteristics and genetic mutation analysis in a family with familial vitreous amyloidosis

Objective

To analyze the clinical characteristics and transthyretin (TTR) gene mutation of a family with familial vitreous amyloidosis (FVA).

Methods

A pedigree investigation was performed.The clinical data of 20 family members of a Han family with FVA treated in the Affiliated Hospital of Guizhou Medical University from May 2005 to March 2019 were collected, including demographic data and ophthalmic examination results.Nine eyes of five patients underwent vitrectomy successively, and vitreous samples collected during operation were sent for pathological examination by Congo red staining.The best corrected visual acuity (BCVA) and intraocular pressure (IOP) were measured, and the anterior segment as well as fundus was observed under the slit lamp microscope at 1 week and 6 months after surgery.Peripheral venous blood (4 ml) was collected from 20 members in this family and DNA was extracted.The next-generation sequencing technology was used for gene detection of proband, and Sanger sequencing was performed in 20 family members including the proband.The pathogenicity of the mutation sites was analyzed according to ACMG guidelines.This study adhered to the Declaration of Helsinki.The study protocol was approved by an Ethics Committee of Affiliated Hospital of Guizhou Medical University (No.2019-296). Written informed consent was obtained from each subject.

Results

The preoperative BCVA of the nine eyes (5 patients) remained 0.1 to 0.2 in 6 eyes, and counting fingers to 50 cm in 3 eyes, and the mean value of preoperative IOP was (15.18±1.32) mmHg (1 mmHg=0.133 kPa). Cotton-wool like opacity in the vitreous and white pedal disc punctate granule on the posterior lens capsule were seen in the 9 eyes under the slit lamp microscope.Vitreous specimens of patients were Congo red stain positive.The BCVA remained 0.8 in 8 eyes and 0.6 in 1 eye at 1 week after vitrectomy, and remained 0.8 in 6 eyes, 0.6 in 2 eyes and light perception in 1 eye at 6 months after surgery.Mean values of postoperative IOP were (15.32±2.11) mmHg and (16.13±1.25) mmHg at 1 week and 6 months after surgery, respectively.Secondary glaucoma occurred in 8 eyes at 3 to 14 years postoperatively.Mean BCVA of the 13 phenotypic normal family members (26 eyes) remained 0.8 to 1.0, and the mean value of IOP was (15.52±1.15) mmHg, and abnormalities were not found in anterior segment or fundus.Additionally, two members (4 eyes) failed to take examinations.Genetic testing revealed heterozygous mutation in p. Gly103Arg of TTR gene in 15 family members.According to ACMG guidelines, the variation score was PS1+ PM2+ PP3, and it was likely pathogenic.

Conclusions

The secondary glaucoma is of relatively high incidence in patients with FVA after vitrectomy.The heterozygous mutation of TTR gene (p.Gly103Arg) might be the variation site of the family with vitreous amyloidosis.

Vitreous amyloidosis; Vitrectomy; Secondary glaucoma; Transthyretin; Genetic mutation; Clinical characteristics; Pedigree study