Early findings in central areolar choroidal dystrophy

The spectrum of retinal dystrophies caused by mutations in the peripherin/RDS gene

Peripherin/rds is an integral membrane glycoprotein, mainly located in the rod and cone outer segments. The relevance of this protein to photoreceptor outer segment morphology was first demonstrated in retinal degeneration slow (rds) mice. Thus far, over 90 human peripherin/RDS gene mutations have been identified. These mutations have been associated with a variety of retinal dystrophies, in which there is a remarkable inter- and intrafamilial variation of the retinal phenotype. In this paper, we discuss the characteristics of the peripherin/RDS gene and its protein product. An overview is presented of the broad spectrum of clinical phenotypes caused by human peripherin/RDS gene mutations, ranging from various macular dystrophies to widespread forms of retinal dystrophy such as retinitis pigmentosa. Finally, we review the proposed genotype-phenotype correlation and the pathophysiologic mechanisms underlying this group of retinal dystrophies.

Genotype-phenotype correlations and differential diagnosis in autosomal dominant macular disease

In the past few years, great progress has been made in the understanding of macular diseases. A number of disease-causing genes have been cloned, and numerous loci for other conditions have been mapped. The purpose of this article is to provide an overview of the current understanding of the genotype-phenotype correlations in autosomal dominant macular diseases with an emphasis on differential diagnostic issues. Whenever possible, the molecular correlates have been reviewed and the implications for age-related macular degeneration have been discussed. The many similarities of these diseases to age-related macular degeneration of the atrophic or exudative type, which can be misleading in elderly subjects, have also been addressed. While some conditions yield disease truly confined to the macula, others show widespread retinal involvement on functional testing. Clear-cut genotype-phenotype correlations are possible only for some forms of macular diseases. To further complicate the diagnostic process, there is a considerable degree of clinical overlap between many of them, making the differential diagnostic process potentially challenging. Functional testing, careful assessment of family history and extensive family work-up are essential in differentiating at the clinical level most, but not all, of these disease entities. Awareness of all of these conditions is required to direct correctly diagnostic investigations, to formulate an accurate prognosis, and for proper genetic counseling.

Differential diagnosis of hereditary pigmentary maculopathies

The hereditary pigmentary macular dystrophies rank among the most challenging diagnostic entities in optometric practice. Patients with these disorders can present with clinical characteristics along a broad spectrum, ranging from normal fundus findings to profound macular changes, with or without reduction in visual function. This paper reviews the key differentiating aspects of this group of disorders, including clinical testing and management strategies.

Central areolar choroidal dystrophy and slowly progressive sensorineural hearing loss

Central areolar choroidal dystrophy (CACD) is a rare hereditary disorder leading to a central scotoma in middle-aged patients. Two cases of CACD in association with perceptive hearing loss are discussed. A 62-year-old male and a 51-year-old female patient complained of visual deterioration and subsequent hearing loss over several years. In addition to routine ophthalmic and otorhinolaryngological examination both patients underwent fluorescein angiography, (electro)physiological examination and audiometry examination. A demarcated area of atrophy of pigment epithelium and choriocapillaris was found in both patients. A slowly progressive sensorineural hearing loss after adolescence was found in both patients. The hearing deteriorated to such a level at middle age that hearing aids were necessary. These two cases show that CACD may be associated with perceptive hearing loss.

Autosomal dominant central areolar choroidal dystrophy caused by a mutation in codon 142 in the peripherin/RDS gene

PURPOSE

Because several macular dystrophies are caused by mutations in the peripherin/RDS gene, we examined autosomal dominant and sporadic cases of central areolar choroidal dystrophy for mutations in the peripherin/RDS gene.

METHODS

DNA sequence analysis of the peripherin/RDS gene was performed in four sporadic cases and in ten affected and nine unaffected individuals from seven families with autosomal dominant central areolar choroidal dystrophy.

RESULTS

An Arg-142-Trp mutation in the peripherin/RDS gene was found in ten affected family members in seven families. Among these, a 69-year-old man with the Arg-142-Trp mutation, who was unaffected six years before blood sample analysis, showed a parafoveal area of chorioretinal atrophy. The 65-year-old sister of this family had the Arg-142-Trp mutation with no macular abnormalities, but she might still develop central areolar choroidal dystrophy at an older age. No mutation was found in the four sporadic cases.

CONCLUSION

Autosomal dominant central areolar choroidal dystrophy, studied in seven families, is caused by an Arg-142-Trp mutation in the peripherin/RDS gene.

Full-field electroretinograms in patients with central areolar choroidal dystrophy

Patients with central areolar choroidal dystrophy are often difficult to diagnose because they are similar in fundus appearance to other retinal disorders. Nineteen patients with the diagnosis were studied in order to estimate the diagnostic and prognostic value of full-field electroretinography in this disorder. Our results showed that the cone b-wave amplitude in the ERG is decreased, that there is a progression in this decrease during a follow-up period of 5 years, and that the cone b-wave implicit time is prolonged. Central areolar choroidal dystrophy is considered to be primarily a choroidal disease. Our results indicate that it also affects most or all of the retinal cones. Further, our observations suggest that the disease is slowly progressive and that full-field electroretinography is of value in its early diagnosis.

A variant of central areolar choroidal dystrophy

This article describes the variable ophthalmoscopic features of a macular disorder in five generations of one family. This disease shares similarities with central areolar choroidal dystrophy and other progressive dominant macular dystrophies but demonstrates significant differences that required further consideration. The milder affected individuals had confluent hyperfluorescence around the macular area while the more severe lesions consisted of marked chorioretinal atrophy of the macula. The visual fields revealed a central scotoma. The disorder was transmitted as an autosomal dominant trait.