Posterior Pole Involvement in Patients affected by Dystrophia Myotonica 1 (DM1): Correlation to Genotype?

Abstract

Purpose : Patients affected by Myotonic Dystrophy Type 1 or Dystrophia myotonica 1 (DM1), also called Curschmann-Steinert disease, show variable multi-systemic manifestations of the disease and variable ocular findings. Cataract and Ptosis are well recognized ocular findings associated with the disease, but the posterior pole can also be affected. We performed a prospective clinical study to determine whether posterior pole involvement is dependent on the genotype.

Methods : Patients diagnosed with DM1 underwent complete ophthalmic examination including multimodal imaging (SD-OCT, color fundus photo, infra-red reflectance, infra-red fluorescence, red-free photographs, SS-OCTA and fundus autofluorescence) of the macula (55°) and optic disc, to detect changes at the posterior pole. Upon written consent, patients underwent genetic testing and the number of CTG triplet repeats in the 3’-untranslated region (3’-UTR) of the DMPK gene was assessed by PCR and Southern blot analysis. More than 49 CTG triplet repeats were considered pathogenic, and the number of triplet repeats was correlated with posterior pole findings.

Results : 16 patients (5 male; 11 female, mean age: 42 ± 15 years) underwent genetic testing and multimodal imaging. 15 patients had ≥ 50 CTG triplet repeats in the 3’-UTR of the DMPK gene and entered the study. Genetic testing revealed a spectrum of 50 – 1000 CTG triplet repeats associated with a variable degree of multi-systemic manifestations (subclinical to severely affected). Posterior pole involvement ranged from normal posterior pole findings to severe maculopathy.

Conclusions : Extensive CTG triplet expansions (up to 1000 repeats) lead to severe multi-systemic manifestations, the posterior pole however appears to be less affected. Patients with CTG triplet expansions at the lower limit (~50 repeats) show subclinical multi-systemic findings but can suffer from severe maculopathy.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.