User:FateAmenableToChange/sandbox/Costeff Optic Atrophy Syndrome

FateAmenableToChange/sandbox/Costeff Optic Atrophy Syndrome
Other names	3-Methylglutaconic Aciduria Type III, Costeff Syndrome, Optic Atrophy Plus Syndrome

Costeff optic-atrophy syndrome, also known as Costeff syndrome, 3-methylglutaconic aciduria (MGA) type III, is a neuro-ophthalmological genetic disorder caused by mutations in the OPA3 gene. It is typically associated with early-onset optic atrophy and later-onset spasticity, movement problems (choreoathetosis), and cognitive deficiency. The disorder is named after Hanan Costeff, the doctor who first described the syndrome in 1989.

Signs and symptoms

The characteristic symptoms of Costeff syndrome is the onset of progressively worsening eyesight within the first few years of childhood, with the majority of affected individuals also developing motor disabilities later in childhood and. Occasionally, people with Costeff syndrome may also experience mild cognitive disability.

Also, a hallmark of the disease is an increased level in the urinary concentrations of 3-methylglutaconic acid and 3-methylglutaric acid, which allows diagnosis as early as one year of age.

Those with Costeff syndrome typically experience the first symptoms of visual deterioration within the first few years of childhood, which manifests as the onset of decreasing visual acuity. Caused by degeneration of the optic nerve (optic atrophy), visual acuity tends to continue to decrease with age.

The majority of people with Costeff syndrome develop movement problems and motor disabilities later in childhood, though typically show the first signs before the age of ten. The two most notable of these are

• Choreoathetosis, which causes involuntary movement involving the erratic, jerky movements of chorea as well as the twisting and writhing movements which characterize athetosis.

• Spasticity (excessive muscle contraction), resulting in twitches and spastic tendencies

These two symptoms are often severe enough to cause major disability; among 36 individuals, 17 experienced major motor disability as a result of choreoathetosis, and 12 experienced spasticity-related symptoms severe enough to do the same.

Ataxia (loss of muscle coordination) and speech impairment caused by dysarthria also occur in roughly 50% of cases, but are rarely seriously disabling.

Some individuals with Costeff disease also display mild cognitive impairment, though such cases are relatively infrequent.

Genetics

Costeff syndrome is an autosomal recessive disorder caused by a mutation in the OPA3 gene, which carries instructions for synthesis of its gene product, the OPA3 protein. The exact function of the product protein is unknown, though it is known to play an integral role in mitochondrial function.

The disorder can be caused by several different mutations in the OPA3 gene. However, nearly all reported cases of Costeff syndrome has been in individuals of Iraqi Jewish origin, all of whom share the same splice site founder mutation, though the severity of symptoms varies with the individual. In particular, it is a G-to-C mutation of a single nucleotide (see single-nucleotide polymorphism) which interferes with gene expression levels.

To date, there have only been two reported cases of Costeff syndrome not due to the founder mutation, each of which was due to a different pathogenic variants (mutation).

Two other OPA3 mutations have also been reported which result in a rare dominant disorder symptoms similar to Costeff syndrome.

Treatment

There is currently no cure for Costeff syndrome. Treatment is supportive, and thus focuses on management of the symptoms. In particular, visual impairment, spasticity, and movement disorder is treated in the same way as similar cases occurring in the general population.

Prognosis

Costeff syndrome appears to have no effect on life expectancy at least up to the fourth decade of life. However, as mentioned previously, movement problems can often be severe enough to confine individuals to a wheelchair at an early age, and both visual acuity and spasticity tend to worsen over time.

Epidemiology

First described in 1989, Costeff syndrome has been reported almost exclusively in individuals of Iraqi Jewish origin with only two exceptions, one of whom was a Turkish Kurdish, with the other being of Indian descent.Within the Iraqi Jewish population, the carrier frequency of the founder mutation is about 1/10, with the prevalence of Costeff syndrome itself estimated at anywhere between 1 in 400 and 1 in 10,000.