Ophthalmological findings in childhood onset myotonic dystrophy type 1

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Abstract Purpose Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic disorder, characterised by increasing severity and anticipation (progressive expansion of the repeat size and earlier onset in successive generations). It is caused by an expanded cytosine‐thymine‐guanine (CTG) triple repeat expansions in the myotonic protein kinase gene located on chromosome 19. Muscle wasting, myotonia and cataract are features of classical DM1, while congenital and childhood DM1 are also present with CNS involvement and cognitive impairments. The aims of the current study were to describe ophthalmological findings in individuals with childhood onset DM1, to correlate the ophthalmological findings with the size of the CTG expansions, inheritance and the age of onset and presenting clinical symptoms. Methods Sixty‐ two children and adolescents were eligible for the study and 49 accepted to participate. All had clinical symptoms <10 years of age and were diagnosed with >40 CTG repeats <18 years of age. According to the age of onset and presenting clinical symptoms, the subjects were divided into three subgroups: I/ severe congenital II/ mild congenital and III/ childhood DM1. Results High hyperopia, heterotropia, subnormal VA, motility abnormalities and nystagmus were common features of congenital onset DM1. No cataract was found and ptosis was rare while pseudoptosis and motility disorders occurred frequently among individuals with high number of CTG repeats. Conclusion Ophthalmological pathology was common and individuals with severe congenital DM1 were present with the highest frequency. Number of CTG repeats affected the motility and pseudoptosis while inheritance had no influence on ophthalmological abnormalities.