Author: Maria Syriga (Greece)
Co-authors: Vasileios Soumplis, Charalampos Kapernopoulos, Dimitris Kleftogiannis, Michael Karampelas
The presence of outer retinal tubulations (ORTs) is a tomographic sign described as round to oval structures with hyper-reflective borders surrounding a relatively hyporeflective cavity and are mainly detected at the outer nuclear layer of the retina. This finding is attributed to the disarrangement of the photoreceptors – mostly cones – that takes place in various degenerating conditions of the retina associating choroidal neovascularization or subretinal fibrosis. Maternally inherited diabetes and deafness (MIDD) comprises a rare form of diabetes and is associated with the m.3243 A > G point mutation in mitochondrial DNA. The accurate recognition should meet one or more of the following criteria; 1) impaired fasting glucose and normal BMI, 2), matrilineal transmission, 3) sensorineural hearing loss, 4) maculopathy and 5) genetic analysis compatible with mutations of mitochondrial genes linked to MIDD. Our aim is to describe the presence of ORTs in a case of a patient with typical MIDD presentation and enrich the currently available data about the formation of these structures in a progressively degenerative entity such as MIDD.
This is a case of a 57-year-old diabetic patient referred to our clinic complaining of mild, bilateral vision loss and difficulty in reading few years prior to her visit.
The patient underwent clinical examination including best-corrected visual acuity (BCVA), anterior segment evaluation, fundoscopy, optical coherence tomography (OCT) as well as audiological evaluation.
BCVA was 8/10 (Snellen) for the right and 9/10 for the left eye. Fundus examination demonstrated diffuse areas of chorioretinal atrophy located in the posterior pole bilaterally in a symmetrical pattern. These areas surrounded the fovea, preserving a central island of normal retina and were accompanied with smaller areas of pigment clumping. OCT demonstrated disruption and loss of photoreceptors and RPE that corresponded with the atrophic areas as well as the presence of a number of ORTs seen as ovoid structures with hyperreflective borders and hyporeflective interior located in the outer nuclear layer of the retina. Follow-up seven months after her initial visit showed no alterations in the clinical and imaging status of the patient. Audiological evaluation revealed severe sensorineural hearing loss affecting high frequencies bilaterally. In the context of family screening, the patient’s sister was also assessed and subsequently diagnosed with pre-diabetes. Her BCVA was 8/10 bilaterally, while fundoscopic examination revealed mild non-proliferative diabetic retinopathy bilaterally and mild RPE changes in the posterior pole. OCT did not show any significant pathology in either eye. Audiological examination revealed a moderate sensorineural hearing loss bilaterally.
MIDD is a rare entity, frequently under- or misdiagnosed by physicians. History of diabetes along with hearing impairment and typical findings in fundoscopic examination should prompt the further investigation for MIDD. Due to its mitochondrial inheritance pattern, a strong family history with the transmission of the mutated mitochondrial DNA from the mother to all the descendants may also contribute to the accurate diagnosis. ORTs are a non-specific finding that can be found in MIDD and other retinal dystrophies, including neovascular age-related macular degeneration and retinitis pigmentosa. To date, a limited number of publications presented the detection of ORTs in MIDD patients. Taking under consideration the extremely low percentage of this entity in the diabetic population and also the possible misdiagnosis in daily clinical practice, the detection of ORTs in a patient with diabetes should raise the possibility of a MIDD diagnosis. Finally, the presence of ORTs in the context of MIDD can set the ground for further population-based studies and investigation of the molecular mechanisms involved in pathophysiology and disease progression.
The authors received no financial support for the research, authorship and/or publication of this work.