Session Title: Imaging II
Session Date/Time: Sunday 29/09/2013 | 08:00-10:00
Paper Time: 08:08
Venue: Hall G1 (Level 2)
First Author: J.Keunen THE NETHERLANDS
Co Author(s): C. Boon P. de Laat J. Smeitink M. Janssen
To describe the spectrum of retinal abnormalities associated with the m.3243A>G mutation in the mitochondrial MTTL1 gene and to analyze putative correlations between the severity of retinal abnormalities and both disease severity in other organ systems and heteroplasmy levels.
Observational, cohort-based, cross-sectional study.
Extensive clinical examinations were performed, including visual acuity testing, indirect ophthalmoscopy, color fundus photography, fundus autofluorescence, high-resolution optical coherence tomography (OCT), and central visual field analysis. In select patients, Goldmann perimetry, fluorescein angiography, full-field electroretinography (ERG) and electro-oculography (EOG), and color vision testing were performed. Heteroplasmy levels of the m.3243A>G mutation were measured in leukocytes, urinary epithelial cells (UEC), and the buccal mucosa. The Newcastle Mitochondrial Disease Adult Scale (NMDAS) score was measured for all patients.
Twenty-five of the 29 mutation carriers (86%) had retinal abnormalities that could be classified into one of four grades. Six patients (21%) had grade 1 retinal dystrophy with fine pigment abnormalities that were clearly visible with fundus autofluorescence and fluorescein angiography. Eleven patients (38%) had grade 2 abnormalities, which were characterized by one (or relatively few) yellowish or mildly pigmented deposits in the early stage; in advanced grade 2, these pigment changes encompassed the entire macula and often encircled the optic disc. Six patients (21%) had grade 3 retinal dystrophy in which profound chorioretinal atrophy was present outside the fovea. The remaining two patients (7%) with retinal abnormalities had a marked loss of visual acuity in grade 4, in which the fovea was affected by atrophy. The grade of mitochondrial retinal dystrophy correlated significantly with both age (r=-0.483, p=0.008) and visual acuity (r=-0.614, p<0.001), whereas no cor relation was observed with either heteroplasmy level or overall disease involvement.
Mitochondrial retinal dystrophy associated with the m.3243A>G mutation has specific characteristics that can be classified into four grades based on the ophthalmoscopy, fundus autofluorescence and OCT findings. However, because the maternal inheritance pattern can be masked and because the systemic disease associations can be variable, atypical, or even absent, the disease can be misdiagnosed.