Eye Blood Vessel Alterations Common in FAP with Val30Met Mutation, Study Finds

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by Alice Melao |

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Blood vessel abnormalities in the eye’s structures are common features in patients with familial amyloid polyneuropathy (FAP) caused by the Val30Met genetic mutation, according to researchers.

Their study, “Angiographic signatures of the predominant form of familial transthyretin amyloidosis (Val30Met mutation),” was published in the American Journal of Ophthalmology.

FAP, or transthyretin (TTR) amyloid polyneuropathy, is a rare disease caused by genetic mutations in the TTR gene.

More than 100 different gene variants have been linked to this disease. The most common, identified as Val30Met mutation, is a substitution of the amino acid valine for methionine in position 30 in the gene sequence.

This disease manifests with a wide range of symptoms including motor and sensory impairment due to nerve damage (neuropathy), as well as heart, renal, and vision problems.

The most common vision problems reported in patients with FAP are glaucoma (high pressure inside the eye that may cause damage to the optic nerve), dryness of the outer layers of the eye, and accumulation of amyloid aggregates in the eye’s structures such as the retina.

To better understand the incidence of ocular manifestations in FAP patients, a team evaluated 18 people with confirmed TTR gene Val30Met mutation.

Of the 18, 13 patients had amyloid depositions in the retina — an inner layer of the eye that has the sensing cells that detect images. These were found to affect the small blood vessels, causing tiny aneurisms, hemorrhages, and obstructions.

Three patients had glaucoma, and two had abnormal formation of new blood vessels. All these alterations are generally known as retinal amyloid angiopathy (RAA).

Among these 13 patients, 11 also had an accumulation of amyloid aggregates inside the eyeball (vitreous).

In addition to these detected retinal amyloid angiopathies (blood vessel disease), all 18 patients had choroidal angiopathy, which are abnormalities in the blood vessels of the outer layer that protects the retina (choroid). The identified changes followed particular patterns: diffuse, focal, or punctiform.

The researchers found that patients with diffuse choroidal angiopathy had higher disability scores compared to patients with limited presentation (focal and punctiform patterns). Also, patients who had retinal blood vessel abnormalities tended to have worse disability scores.

Collectively, these findings suggest that retinal and choroidal angiopathies are common eye complications of FAP caused by the Val30Met mutation. These severe manifestations that may progressively lead to blindness “may be present at various stages of the disease,” researchers said.

Recognizing these particular features “may help diagnose FAP in patients with no familial history or unexplained vitreous opacities [protein aggregates],” they added.