achromatopsia

Jalili Syndrome

Clinical Characteristics
Ocular Features: 

Symptoms of photophobia and reduced vision are present in the first years of life.  Pendular nystagmus is common.  Color vision is defective and is characterized by some as a form of achromatopsia, perhaps better described as dyschromatopsia.  Reduced night vision is noted by the end of the first decade of life.  OCT reveals reduced foveal and retinal thickness.  The macula appears atrophic with pigment mottling and the peripheral retina can resemble retinitis pigmentosa with bone spicule pigment changes.  Retinal vessels may be narrow.  The ERG shows reduced responses in both photopic and scotopic recordings.  This form of rod-cone dystrophy is progressive with central acuity decreasing with age. 

Systemic Features: 

The teeth are abnormally shaped and discolored from birth.  The amelogenesis imperfecta consists of hypoplasia and hypomineralization that is present in both deciduous and permanent teeth.  Tooth enamel is mineralized only to 50% of normal and is similar to that of dentine. 

Genetics

This is an autosomal recessive condition caused by mutations in the CNNM4 gene at 2q11.2. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment is available for the ocular condition but red-tinted lenses and low vision aids may be helpful.  The teeth require dental repair. 

References
Article Title: 

Mutations in CNNM4 cause Jalili syndrome, consisting of autosomal-recessive cone-rod dystrophy and amelogenesis imperfecta

Parry DA, Mighell AJ, El-Sayed W, Shore RC, Jalili IK, Dollfus H, Bloch-Zupan A, Carlos R, Carr IM, Downey LM, Blain KM, Mansfield DC, Shahrabi M, Heidari M, Aref P, Abbasi M, Michaelides M, Moore AT, Kirkham J, Inglehearn CF. Mutations in CNNM4 cause Jalili syndrome, consisting of autosomal-recessive cone-rod dystrophy and amelogenesis imperfecta. Am J Hum Genet. 2009 Feb;84(2):266-73.

PubMed ID: 
19200525

Cone-Rod Dystrophies, X-Linked

Clinical Characteristics
Ocular Features: 

Three X-linked forms of progressive cone-rod dystrophies each with mutations in different genes have been identified.  Central vision is often lost in the second or third decades of life but photophobia is usually noted before vision loss.  Cones are primarily involved but rod degeneration occurs over time.  The ERG reveals defective photopic responses early followed by a decrease in rod responses.   All three types are rare disorders affecting primarily males with symptoms of decreased acuity, photophobia, loss of color vision, and myopia.  The color vision defect early is incomplete but progressive cone degeneration eventually leads to achromatopsia.    Peripheral visual fields are usually full until late in the disease when constriction and nightblindness are evident.  The retina may have a tapetal-like sheen.  RPE changes in the macula often give it a granular appearance and there may be a bull's-eye configuration.   Fine nystagmus may be present as well.  The optic nerve often has some pallor beginning temporally.  Carrier females can have some diminished acuity, myopia, RPE changes, and even photophobia but normal color vision and ERG responses at least among younger individuals.

There is considerable variation in the clinical signs and symptoms in the X-linked cone-rod dystrophies among both affected males and heterozygous females.  Visual acuity varies widely and is to some extent age dependent.  Vision can be normal into the fourth and fifth decades but may reach the count fingers level after that. 

Systemic Features: 

None.

Genetics

Mutations in at least 3 genes on the X chromosome cause X-linked cone-rod dystrophy.

CORDX1 (304020) is caused by mutations in an alternative exon 15 (ORG15) of the RPGR gene (Xp11.4) which is also mutant in several forms of X-linked retinitis pigmentosa (300455, 300029).  These disorders are sometimes considered examples of X-linked ocular disease resulting from a primary ciliary dyskinesia (244400).

CORDX2 (300085) is caused by mutations in an unidentified gene at Xq27.  A single family has been reported.

CORDX3 (300476) results from mutations in CACNA1F.  Mutations in the same gene also cause a form of congenital stationary night blindness, CSNB2A (300071).  The latter, however, is a stationary disorder with significant nightblindness and mild dyschromatopsia, often with an adult onset, and is associated with high myopia. Aland Island Eye Disease (300600) is another allelic disorder.   

Pedigree: 
X-linked dominant, father affected
X-linked dominant, mother affected
X-linked recessive, carrier mother
X-linked recessive, father affected
Treatment
Treatment Options: 

There is no treatment for these dystrophies but red-tinted lenses provide comfort and may sometimes improve acuity to some extent.  Low vision aids can be helpful. 

References
Article Title: 
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