Avellino corneal dystrophy is a rare, inherited eye condition that impacts the cornea, the transparent, dome-shaped outer layer at the front of the eye. This progressive disorder leads to reduced visual clarity due to the gradual accumulation of abnormal protein deposits within the corneal tissue. As these deposits increase in size and number, they can interfere with light passing through the cornea, resulting in various degrees of vision impairment.
What is Avellino Corneal Dystrophy?
Avellino corneal dystrophy is also known as Granular Corneal Dystrophy Type 2 (GCD2) or combined granular-lattice corneal dystrophy. The name “Avellino” originates from the Italian province where the condition was first identified in families with both granular and lattice corneal disease features. This dystrophy is characterized by the coexistence of two distinct types of protein deposits within the cornea: granular and lattice-like opacities.
The granular deposits appear as small, whitish, crumb-like dots, primarily in the anterior and superficial stromal layers of the cornea. Over time, fusiform amyloid deposits, similar to those seen in lattice corneal dystrophy, can develop in the deeper stromal layers. These deposits accumulate over decades, starting in early childhood, progressively reducing corneal clarity and vision.
Identifying the Symptoms
Symptoms of Avellino corneal dystrophy vary in onset and severity. Early symptoms can be subtle and may include discomfort from bright light, known as photophobia, and glare. Mild blurring of vision might also be noticed as initial deposits begin to form in the cornea.
As the condition advances and more deposits accumulate, vision changes become more noticeable and can progress to significant vision loss. Patients may also experience a foreign body sensation in the eye due to the irregular corneal surface. Recurrent corneal erosions, small abrasions on the eye’s surface, are also common and can cause sharp pain, especially upon waking.
The Genetic Connection
Avellino corneal dystrophy is an inherited disorder caused by specific mutations in the TGFBI gene on chromosome 5. This gene provides instructions for producing transforming growth factor beta-induced protein (TGFBIp). TGFBIp is an extracellular matrix protein involved in maintaining corneal structure and health.
A common mutation is the R124H mutation in the TGFBI gene. This genetic alteration leads to the production of an abnormal TGFBIp, which then accumulates as insoluble deposits within the corneal layers. The condition follows an autosomal dominant inheritance pattern, meaning that only one copy of the mutated gene is sufficient for the disorder to develop. This implies that an affected individual has a 50% chance of passing the mutated gene to each of their children, regardless of gender.
Diagnosis and Management
Diagnosis of Avellino corneal dystrophy involves a comprehensive eye examination performed by an ophthalmologist. A slit-lamp examination is a standard method, allowing the clinician to visualize the characteristic granular and lattice-like deposits within the corneal layers. These deposits may appear as discrete white dots, often with interspersed linear opacities. Genetic testing can provide a definitive diagnosis by identifying the TGFBI gene mutation. It is also valuable for screening family members at risk.
Management strategies for Avellino corneal dystrophy range from conservative measures to surgical interventions, depending on the severity of symptoms and the extent of corneal involvement. For mild cases, lubricating eye drops can help manage dryness and discomfort. Special contact lenses may be prescribed to improve vision if irregular astigmatism develops due to the corneal changes. When vision is significantly impaired by superficial deposits, phototherapeutic keratectomy (PTK) may be performed. This laser procedure aims to remove the deposits from the anterior corneal layers, potentially improving visual acuity.
For more advanced cases where deposits are deeper or widespread, corneal transplant procedures become an option. These include penetrating keratoplasty (PKP), which involves replacing the entire central cornea, or deep anterior lamellar keratoplasty (DALK), which replaces only the diseased stromal layers while preserving the innermost corneal layer. Even after surgical intervention, the abnormal protein deposits can recur within the grafted cornea over time, necessitating ongoing monitoring and potential further treatment.