Primary cataract as a key to recognition of myotonic dystrophy type 1

Primary cataract is often the initial manifestation of the adult-onset type of myotonic dystrophy type 1 (DM1), the most common muscular dystrophy in adults. It is caused by a CTG repeat expansion within the DMPK gene, and anticipation may cause earlier onset and more severe symptoms in subsequent generations.

We report a family with hereditary cataract, which was initially classified as primary hereditary cataract. After presentation of 2 children with motor development delay and behavioral changes, DM1 was diagnosed. Subsequently, various DM1 features were recognized in older family members.

This report aims to increase awareness among ophthalmologists of the high prevalence of DM1 among young primary cataract patients. Ophthalmologists can play a significant role in early diagnosis, since cataract frequently is the first occasion that patients seek medical attention. Early recognition is crucial since it enables adequate cardiac follow-up and allows counseling of couples of childbearing age.