This 66YO female was seen for a diabetic retinopathy screening. She had a prior history of age-related macular degeneration (AMD). There were no visual symptoms. Vision was 20/40 OD and 20/30 OS.
Optos color RGB imaging shows moderate non-proliferative diabetic retinopathy (NPDR) with some scattered retinal hemorrhages and nerve fiber layer infarcts. Some focal areas of non-central macular atrophy are also seen.
Fundus autofluorescence (FAF) shows hypo-FAF from the areas of atrophy, along with areas of hyper-FAF around each nerve and macula.
Swept-source OCT shows outer retinal and RPE atrophy. A small area of outer retinal tubulation (ORT) is noted along the edge of an area of atrophy OD.
On further questioning, the patient’s mother had type 2 diabetes. Hearing was normal in our patient and her mother. Genetic testing of our patient showed a pathologic mitochondrial A3243G mutation.
Learning Points:
Maternally inherited diabetes and deafness (MIDD) accounts for up to 3% of all cases of diabetes and results from a mutation in mitochondrial DNA at position A3243G. MIDD often masquerades as a pattern macular dystrophy.
In our experience, fundus autofluorescence (FAF) is the best way to visualize these changes. The FAF appearance somewhat resembles that seen with Elmiron toxicity. Peripapillary hypoautofluorescence, more densely packed macular autofluorescent changes, and earlier central macular involvement suggest Elmiron toxicity over other causes (see Barnes et al Ophthalmology Retina 2020;4:1196-1201).
ORT is often noted overlying inactive MNV with ongoing anti-VEGF therapy and should not be confused with exudative fluid or cysts, which lack a hyperreflective border. The outer hyperreflective band likely represents inner segment mitochondria undergoing fission and translocation toward the nucleus (Litts et al, Retina 2018;38:445-461).
ORT, initially described by Zweifel et al (Arch Ophthalmol 2009;127:1596-1602), is a neurodegenerative condition of the photoreceptors and Muller cells associated with atrophy affecting the outer retina and retinal pigment epithelium, including advanced AMD and inherited retinal diseases.
