Clinical Description
Most individuals with Costeff syndrome present within the first ten years of life with decreased visual acuity and/or choreoathetoid movement disorder. Although most develop spastic paraparesis, mild ataxia, and occasional mild cognitive deficit in their second decade, the course of the disease is relatively stable.
The following description of the phenotypic features of Costeff syndrome is based on two reports:
Elpeleg et al [1994] reported on 36 affected individuals, 11 of whom were previously unreported and 25 of whom had been previously reported.
Optic Atrophy
Optic atrophy manifests as decreased visual acuity within the first years of life, sometimes associated with infantile-onset horizontal nystagmus.
In 36 individuals with Costeff syndrome, visual acuity decreased with age:
In two children age two years, visual acuity appeared to be normal.
In 14 individuals age three to 21 years (14.2±5.5), visual acuity was 6/21 or less.
In 20 individuals age five to 37 years (18±9.5), visual acuity was 3/60 or less.
Some children have strabismus and gaze apraxia.
Motor Disability
Motor disability is primarily caused by extrapyramidal dysfunction and spasticity.
Extrapyramidal dysfunction. Most individuals have chorea, often severe enough to restrict ambulation. Some are confined to a wheelchair from an early age. In 36 individuals with Costeff syndrome, extrapyramidal involvement caused the following in 32 individuals:
Major disability in 17 individuals age two to 37 years (mean 16.1±17.8)
Minor disability in maintaining stable posture and fine motor activities in 12 individuals age two to 26 years (11.7±8.1)
Mild manifestations with no resulting disability in three individuals age 15 to 36 years
No extrapyramidal involvement was observed in four individuals ages 13 to 32 years.
Spasticity. Unstable spastic gait, increased tendon reflexes, and Babinski sign may be seen. In 36 individuals with Costeff syndrome, spasticity was age-related:
Nine individuals age two to 12 years (5.9±3.5) did not have spasticity.
Four individuals age 11 to 26 years had mild spasticity but no related disability.
Eleven individuals age 13 to 37 years (21.4±9.3) had mild spasticity-related disability.
Twelve individuals age nine to 26 years (17.0±4.8) had severe spasticity-related disability.
Cerebellar dysfunction is usually mild. Ataxia and dysarthria caused mostly mild disability in 18 of the 36 individuals reported by Elpeleg et al [1994].
Cognitive Impairment
Cognitive impairment was previously noted in some individuals. Of 36 individuals:
Nineteen individuals age two to 36 years (16±18.7) had an IQ of 71 or higher.
Thirteen individuals age two to 37 years (14.7±9.2) had an IQ between 55 and 71.
Four individuals age nine to 26 years had an IQ between 40 and 54.
More recently, however, a study of the neuropsychological profile of 16 adults with Costeff syndrome reported intact global cognition and learning abilities and strong auditory memory performance [Sofer et al 2015].
Other
Several affected individuals were reported to have married, four of whom (all female) had healthy offspring [Yahalom et al 2014].
Affected adults in the seventh decade of life have been reported [Yahalom et al 2014]; life expectancy beyond the seventh decade is unknown.
Seizures are not typical in Costeff syndrome. Partial seizures were reported in one individual. In addition, two individuals with Costeff syndrome were reported with electrical status epilepticus during slow-wave sleep (ESESS) (also known as continuous spike-wave of slow sleep (CSWSS) [Carmi et al 2015, Kessi et al 2018].
Cranial nerve functions, sensation, and muscle tone are normal.
No cardiac or structural brain abnormalities have been reported.
The level of 3-methylglutaconate (3-MGC) or 3-methylglutaric acid (3-MGA) in urine does not correlate with the degree of neurologic damage.
Electroretinogram is normal.
Genotype-Phenotype Correlations
Genotype-phenotype correlations cannot be made due to the limited number of OPA3 pathogenic variants identified to date.
All individuals of Iraqi Jewish origin with Costeff syndrome have the same pathogenic variant (c.143-1G>C); however, phenotypic severity varies, even within the same family.
Prevalence
Costeff syndrome has been reported in more than 40 individuals of Iraqi Jewish origin [Anikster et al 2001], but also in families of Kurdish-Turkish descent [Kleta et al 2002], Afghani descent [Gaier et al 2019], and others. Of note, as the vast majority of affected individuals are still of Iraqi Jewish descent residing in Israel, it must be underscored that some families originate from the Iraqi area, including Iran and Syria. Individuals with Costeff syndrome have also been diagnosed from outside of Israel, including recently in the United States [Author, personal observation].
The carrier rate in Iraqi Jews was initially estimated at 1:10 [Anikster et al 2001]; however, subsequent screening tests showed the carrier rate to be 1:20-1:30 [Author, personal observation].