loss of photoreceptors

Infantile Cerebellar-Retinal Degeneration

Clinical Characteristics
Ocular Features: 

Visual tracking can be normal during the newborn period but lack of visual fixation and attention soon become evident.  Strabismus, nystagmus, and abnormal pursuit movements are often present.  Optic atrophy has been reported as early as 3 years of age.  VEP and ERG responses are extinguished in the first two years. The nystagmus may be multidirectional.  Acuity loss seems to be progressive.  A progressive retinal degeneration (not further characterized) has been reported.

Systemic Features: 

Infants generally appear normal at birth.  Within the first 6 months they show signs of developmental delay and neurological signs such as truncal hypotonia, seizures, athetosis and head bobbing.  Milestones of sitting, rolling over, and reactions to others are seldom achieved.  Cerebellar brain imaging shows progressive atrophy in all patients and some have cortical atrophy as well.  Some patients have evidence of hearing loss.   Severe failure to thrive and psychomotor delays are usually present.  Death may occur within several months of birth although some live for several decades.

Genetics

This condition results from homozygous or compound heterozygous mutations in the ACO2 gene (22q13.2).  The mutation has also been associated with optic atrophy 9 (616289).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment beyond supportive care is known.

References
Article Title: 

Mutations in the tricarboxylic acid cycle enzyme, aconitase 2, cause either isolated or syndromic optic neuropathy with encephalopathy and cerebellar atrophy

Metodiev MD, Gerber S, Hubert L, Delahodde A, Chretien D, Gerard X, Amati-Bonneau P, Giacomotto MC, Boddaert N, Kaminska A, Desguerre I, Amiel J, Rio M, Kaplan J, Munnich A, Rotig A, Rozet JM, Besmond C. Mutations in the tricarboxylic acid cycle enzyme, aconitase 2, cause either isolated or syndromic optic neuropathy with encephalopathy and cerebellar atrophy. J Med Genet. 2014 Dec;51(12):834-8.

PubMed ID: 
25351951

Retinitis Pigmentosa 71

Clinical Characteristics
Ocular Features: 

Night blindness is noted in the first or second decades of life.  The fundus picture in this condition resembles classic retinitis pigmentosa with attenuated vessels, RPE anomalies with bone spicule clumping and areas of atrophy, and optic disc pallor.  Several patients had optic nerve drusen.  The retina appears to have microcysts, especially in the macula, and the outer retina is thinned.  

Systemic Features: 

Only a few patients have been reported with this form of RP and the full phenotype is unknown.  Some individuals are obese and one patient in addition had postaxial polydactyly and hypercholesterolemia suggestive of a Bardet-Biedl-like phenotype.  No reported patients have had rib dysplasia.

Genetics

Homozygous or compound heterozygous mutations in the IFT172 gene (2p23.3) have been identified in this condition.

The same gene is mutated in the recessive short-rib thoracic dysplasia 10 syndrome with or without polydactyly (615630).  Individuals with the short-rib syndrome may have night blindness and fundus changes resembling retinitis pigmentosa.

Because of the phenotypic overlap with other conditions such as Bardet-Biedl syndrome, the short-rib thoracic 10 syndrome (615630), Majewski syndrome (263520), Jeune syndrome (208520), short-rib thoracic dysplasia 9 (266920), and certain types of polycystic diseases of the kidney with abnormalities of the cilia, it has been suggested that RP71 should be classified as a syndromic ciliopathy.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Mutations in IFT172 cause isolated retinal degeneration and Bardet-Biedl syndrome

Bujakowska KM, Zhang Q, Siemiatkowska AM, Liu Q, Place E, Falk MJ, Consugar M, Lancelot ME, Antonio A, Lonjou C, Carpentier W, Mohand-Said S, den Hollander AI, Cremers FP, Leroy BP, Gai X, Sahel JA, van den Born LI, Collin RW, Zeitz C, Audo I, Pierce EA. Mutations in IFT172 cause isolated retinal degeneration and Bardet-Biedl syndrome. Hum Mol Genet. 2015 Jan 1;24(1):230-42.

PubMed ID: 
25168386
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