Lattice corneal dystrophy type II
Lattice corneal dystrophy type II is a rare, progressive condition characterized by the systemic accumulation of amyloid deposits that primarily affect the eyes, nerves, and skin.
Overview
Lattice corneal dystrophy type II involves the accumulation of protein clumps known as amyloid deposits in tissues throughout the body. These deposits frequently form in blood vessel walls and basement membranes, leading to symptoms that worsen with age.
Symptoms
The condition typically manifests in stages:
- Eye Involvement: Usually appearing in a person's twenties, amyloid deposits form in the stromal layer of the cornea as delicate, branching fibers in a lattice pattern. This clouds the cornea, leading to vision impairment, recurrent painful corneal erosions, and sensitivity to bright light (photophobia). These symptoms are typically bilateral.
- Nerve Involvement: Typically starting in a person's forties, amyloid deposits disrupt nerve function. This can cause facial palsy, facial hypoesthesia, and difficulty speaking, chewing, or swallowing. Peripheral neuropathy may also occur, leading to muscle weakness, clumsiness, and loss of sensation in the limbs.
- Skin Involvement: Also beginning in a person's forties, individuals may experience thickened, sagging skin, dry and itchy skin, or cutis laxa (loose skin lacking elasticity). Facial muscle paralysis combined with loose skin can result in a sad facial expression.
Causes
The condition is caused by mutations in the GSN gene, which provides instructions for making the protein gelsolin. Mutations result in an abnormal gelsolin protein fragment that is released from cells, clumps together, and forms the amyloid deposits responsible for the disease's symptoms.
Inheritance
This condition is inherited in an autosomal dominant pattern. While one copy of the altered gene is sufficient to cause the disorder, individuals with mutations in both copies typically experience more severe signs and symptoms.