SNP Shot: Genomic Insights

Lattice corneal dystrophy type II involves the buildup of abnormal protein clumps, known as amyloid deposits, throughout the body's tissues. These deposits frequently appear in blood vessel walls and basement membranes, the thin layers supporting cells in many tissues. These amyloid buildups result in characteristic symptoms affecting the eyes, nerves, and skin, which worsen over time.

The first sign of this condition, often noticed in a person's twenties, is amyloid deposit accumulation in the cornea, leading to lattice corneal dystrophy. The cornea, the eye's clear outer layer, consists of multiple tissue layers. In lattice corneal dystrophy type II, amyloid deposits form within the stromal layer, creating delicate, branching fibers that resemble a lattice. These protein deposits cloud the cornea, commonly leading to impaired vision. Furthermore, affected individuals may experience recurring corneal erosions, caused by the separation of corneal layers. These erosions are very painful and can cause sensitivity to light (photophobia). Amyloid deposits and corneal erosions typically affect both eyes (bilateral).

As lattice corneal dystrophy type II progresses, nerve involvement typically begins in a person's forties. It's believed that amyloid deposits interfere with nerve function. Dysfunction of cranial nerves, those in the head and face, can cause facial muscle paralysis (facial palsy), decreased facial sensation (facial hypoesthesia), and difficulties with speech, chewing, and swallowing. Dysfunction of peripheral nerves, which connect the brain and spinal cord to muscles and sensory cells, can cause sensation loss and weakness in the limbs (peripheral neuropathy). Peripheral neuropathy usually affects the lower legs and arms, resulting in muscle weakness, clumsiness, and impaired vibration sensation.

The skin is also commonly affected in individuals with lattice corneal dystrophy type II, generally starting in a person's forties. Affected individuals may develop thickened, sagging skin, especially on the scalp and forehead, along with cutis laxa, characterized by loose skin lacking elasticity. The skin may also become dry and itchy. Due to loose skin and facial muscle paralysis, individuals with lattice corneal dystrophy type II may exhibit a sad facial expression.

Inheritance:

This condition follows an autosomal dominant inheritance pattern, meaning that only one copy of the altered gene in each cell is needed to cause the disorder. While a mutation in one copy can cause the disorder, individuals with mutations in both copies of the gene tend to have more severe signs and symptoms.