Myotonic Dystrophy with Reticular Maculopathy as First Ocular Symptom

Introduction

Myotonic dystrophy type 1 (DM1), known also as Curschmann-Steinert syndrome is the most common adult muscular dystrophy. This autosomal dominant transmitted genetic disorder is caused by an instable polynucleotide (CTG)_n triplet expansion in the dystrophia myotonica protein kinase (DMPK) gene, located on chromosome 19 (19q13.2-q13.3). Differing time of onset has led to the following classification in categories: congenital, childhood-onset, adult-onset and late-onset. DM1 is characterized by progressive myopathy attended with multiorgan involvement. Manifestations include myotonia, distal muscular dystrophy, ocular pathologies, cardiac conduction defects, minor intellectual deficits, gastrointestinal tract involvement such as irritable bowel syndrome, symptomatic gall stones or gamma-glutamyltransferase elevations and endocrine abnormalities including testicular atrophy, type-2 diabetes as well as thyroid dysfunctions [1], [2], [3]. Ocular findings in this disorder reported to date are cataract, ptosis, exposure keratitis, strabismus, abnormal dark adaptation, pathological electroretinography, epiretinal fibroplasia, low intraocular pressure and retinal degenerations [4], [5]. The most common ocular manifestation is early cataract development. The first signs of cataract can usually already be detected in the fourth decade of life. Myotonic cataract has been commonly described as lenticular iridescent or punctate opacities, but also other phenotypes of cataract have been reported [6], [7]. The less frequently recorded retinal manifestations have been documented as peripheral pigmentary retinopathy and different presentations of macular dystrophy [7], [8].The commonly used terms reticular-, pattern type- or butterfly shaped macular dystrophy for describing the macular findings in Curschmann-Steinert syndrome can often not be distinguished correctly due to similarities in appearance. The terms might be used equivalently because precise distinction between the terms seems not to be possible. In this case maculopathy shows alterations of the retinal pigment epithelium resembling phenotypically an early manifestation of age-related macular degeneration.

• References

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