Abstract
BackgroundDanon disease is a neuromuscular disorder with variable expression in the eye. We describe a family with Danon disease and cone-rod dystrophy (CRD).MethodsAffected males of one family with Danon were invited for an extensive ophthalmologic examination, including color vision testing, fundus photography, Goldmann perimetry, full-field electroretinogram (ERG), and SD-OCT. Previous ophthalmologic data were retrieved from medical charts. The LAMP2 and RPGR gene were analyzed by direct sequencing.ResultsTwo siblings had no ocular phenotype. The third sibling and a cousin developed CRD leading to legal blindness. Visual acuity deteriorated progressively over time, color vision was severely disturbed, and ERG showed reduced photopic and scotopic responses. SD-OCT revealed thinning of the photoreceptor and RPE layer. Visual fields demonstrated central scotoma. The causal mutation was p.Gly384Arg in LAMP2; no mutations were found in RPGR.ConclusionsThis is the first description of CRD in Danon disease. The retinal phenotype was a late onset but severe dystrophy characterized by loss of photoreceptors and RPE cells. With this report, we highlight the importance of a comprehensive ophthalmologic examination in the clinical work-up of Danon disease.
Highlights
Danon disease is a rare genetic condition caused by mutations in the X-linked (XL) lysosome-associated membrane protein gene (LAMP2)
Gly384Arg in LAMP2; no mutations were found in RPGR. This is the first description of cone-rod dystrophy (CRD) in Danon disease
We highlight the importance of a comprehensive ophthalmologic examination in the clinical work-up of Danon disease
Summary
Danon disease is a rare genetic condition caused by mutations in the X-linked (XL) lysosome-associated membrane protein gene (LAMP2). Retinal abnormalities were reported; detailed work-up including psychophysical testing was lacking [1, 3,4,5]. It was unclear which retinal cell types were affected, whether it included rods and cones, and whether the disease progressed to legal blindness. We present the results of a comprehensive ophthalmologic examination in a small Danon family with cone-rod dystrophy (CRD) due to an uncommon missense mutation in LAMP2. Methods Affected males of one family with Danon were invited for an extensive ophthalmologic examination, including color vision testing, fundus photography, Goldmann perimetry, full-field electroretinogram (ERG), and SD-OCT. The LAMP2 and RPGR gene were analyzed by direct sequencing
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