Choroidal Dystrophy, Central Areolar

Clinical Characteristics
Ocular Features: 

The primary feature of this form of macular dystrophy is atrophy of the RPE and choriocapillaris in the central macula.  In early stages among young patients in the second decade of life, some pigment changes are seen in the parafoveal area.  Later, the central macula develops hypopigmentation followed by atrophy of the choriocapillaris.  The area is usually sharply defined but fluorescein angiography often shows multiple window defects beyond the edges.  The same region often has speckled autofluorescence.  Secondary dysfunction of the photoreceptors in this area leads to some mild degree of vision loss in adults between the ages of 30 and 60 years but this progressive disease may eventually result in legal blindness.  The ERG demonstrates a cone dystrophy. The rate of disease progression is highly variable.  Visual acuity varies considerably as does the appearance of the macula.  Older individuals may be misdiagnosed as having age-related macular degeneration. 

Systemic Features: 

There is no associated systemic disease. 

Genetics

This is a genetically heterogeneous disorder with mutations in several genes responsible.  The majority of patients have one of several mutations in the PRPH2 gene (6p21.1-cen) and the inheritance pattern seems to be autosomal recessive (CACD2).  Other family trees in which mutations in PRPH2 were excluded suggest autosomal dominant inheritance (CACD3; 613144).  CACD1 is caused by an unknown mutation localized to 17p13. 

The gene product of PRPH2 is active in the retina. It is important to the integrity and stability of the structures that contain light-sensitive pigments (e.g., photoreceptors). More than 100 mutations have been identified. The resultant phenotype can be highly variable, even within members of the same family but most affected individuals have some degree of pigmentary retinopathy within the macula or throughout the posterior pole.

The altered gene product resulting from mutations in PRPH2 often leads to symptoms beginning in midlife as a result of the slow degeneration of photoreceptors. This database contains at least 11 disorders in which PRPH2 mutations have been found.

Treatment
Treatment Options: 

There is no treatment of the macular disease.  However, some patients can benefit from low vision aids. 

References
Article Title: 

Central areolar choroidal dystrophy

Boon CJ, Klevering BJ, Cremers FP, Zonneveld-Vrieling MN, Theelen T, Den Hollander AI, Hoyng CB. Central areolar choroidal dystrophy. Ophthalmology. 2009 Apr;116(4):771-82, 782.e1.

PubMed ID: 
19243827

References

Ouechtati F, Belhadj Tahar O, Mhenni A, Chakroun S, Chouchene I, Oueslati S, Rebai A, Abdelhak S, Jeddi-Blouza A. Central areolar choroidal dystrophy associated with inherited drusen in a multigeneration Tunisian family: exclusion of the PRPH2 gene and the 17p13 locus. J Hum Genet. 2009 Oct;54(10):589-94.

PubMedID: 19696794

Boon CJ, Klevering BJ, Cremers FP, Zonneveld-Vrieling MN, Theelen T, Den Hollander AI, Hoyng CB. Central areolar choroidal dystrophy. Ophthalmology. 2009 Apr;116(4):771-82, 782.e1.

PubMedID: 19243827

Lotery AJ, Ennis KT, Silvestri G, Nicholl S, McGibbon D, Collins AD, Hughes AE. Localisation of a gene for central areolar choroidal dystrophy to chromosome 17p. Hum Mol Genet. 1996 May;5(5):705-8.

PubMedID: 8733141