Unique and progressive retinal degeneration in a patient with cancer associated retinopathy.

PURPOSE: To report clinical course of a patient with cancer-associated retinopathy (CAR) medicated by steroid therapy, focusing on retinal degeneration progression. OBSERVATIONS: A 67 years-old female patient, who had a surgical history of endometrial carcinoma with adjuvant chemotherapy, was referred to our hospitals for the complaints of sudden reduced visual acuity and visual field constriction in the right eye. Best corrected visual acuity (BCVA) was 0.4 and 1.0 in right and left eyes, respectively. Funduscopy showed almost normal appearance in both eyes. Fluorescein angiography showed slight fluorescein leakage from the optic disc in both eyes and an inferior arcade vessel in the right eye. Optical coherence tomography (OCT) images showed loss of ellipsoid zone (EZ) and thinning of outer retinal layers at the nasal area of the fovea in both eyes. Goldmann perimetry (GP) demonstrated several paracentral absolute scotomas with peripheral visual field constriction in the right eye, and a paracentral relative scotoma with preserved peripheral visual field in the left eye. Ten months after the first visit, retinopathy progressed in both eyes. Funduscopy indicated mild retinal degeneration along with arcade veins with white sheathing of retinal arteries. Slightly visible EZ at the fovea and loss of EZ and interdigitation zone and thinning of outer retinal layers at other areas were observed in OCT images from both eyes. GP showed no response in both eyes. Oral prednisolone therapy was started and gradually tapered over a 3-month period. Twelve and fifteen months after the first visit, BCVA, EZ at the fovea in OCT images, and visual field gradually improved, whereas retinal degeneration along arcade veins became apparent. CONCLUSIONS AND IMPORTANCE: We reported a patient with CAR who exhibited progressive retinal degeneration and good response to oral prednisolone therapy. This case expands the clinical spectrum of CAR.

Improvement of reduced electroretinographic responses in thymoma-associated retinopathy: a case report and literature review.

PURPOSE: To report a patient with thymoma-associated retinopathy presenting as having a good visual prognosis. METHODS: Case report and literature review. CASE REPORT: A 42-year-old female patient was referred to our hospital for complaints of sudden visual-field defects bilaterally. Decimal corrected visual acuity (VA) was 1.5 and 1.2 in the right (RE) and left eyes (LE), respectively. Fundus autofluorescence revealed hyper-autofluorescence from the posterior pole to mid-peripheral retina in both eyes. Full-field electroretinography (ERG) amplitudes were reduced to 20-50% and 30-50% of our controls for the scotopic and photopic conditions, respectively. A systemic examination revealed the presence of thymoma, and the patient underwent thymectomy and immunosuppression therapies. Immunohistochemical analysis using the patient's serum showed immunolabeling on the photoreceptor inner segment and outer plexiform layer in the monkey retina. Two years later, VA remained at 1.5 and 1.2 in RE and LE. ERG amplitudes improved to 30-60% of the controls for the scotopic conditions. However, photopic ERG showed no remarkable change. CONCLUSIONS: To our knowledge, improvement of reduced rod-mediated ERG responses has not been described in seven previously reported patients with thymoma-associated retinopathy. The good visual prognosis of our patient may be associated with well-timed intervention.

Targeted inactivation of synaptic HRG4 (UNC119) causes dysfunction in the distal photoreceptor and slow retinal degeneration, revealing a new function.

HRG4 (UNC119) is a photoreceptor protein predominantly localized to the photoreceptor synapses and to the inner segments to a lesser degree. A heterozygous truncation mutation in HRG4 was found in a patient with late onset cone-rod dystrophy, and a transgenic (TG) mouse expressing the identical mutant protein developed late onset retinal degeneration, confirming the pathogenic potential of HRG4. Recently, the dominant negative pathogenic mechanism in the TG model was shown to involve increased affinity of the truncated mutant HRG4 for its target, ARL2, which leads to a delayed decrease in its downstream target, mitochondrial ANT1, mitochondrial stress, synaptic degeneration, trans-synaptic degeneration, and whole photoreceptor degeneration by apoptosis. In this study, the mouse HRG4 (MRG4) gene was cloned and targeted to construct a knock-out (KO) mouse model of HRG4 in order to study the effects of completely inactivating this protein. The KO model was examined by genomic Southern blotting, Western blotting, immunofluorescence, funduscopy, LM and EM histopathology, ERG, and TUNEL analyses. The KO model developed a slowly progressive retinal degeneration, characterized by mottling in the fundus, mild thinning of the photoreceptor layer, and increase in apoptosis as early as 6 months, dramatic acceleration at approximately 17 months, and virtual obliteration of the photoreceptors by 20 months. When compared to retinal degeneration in the TG model, significant differences existed in the KO consisting of more severe and early photoreceptor death without evidence of early synaptic and trans-synaptic degeneration as seen in the TG, confirmed by LM and EM histopathology, ERG, and Western blotting of synaptic proteins. The results indicated a dysfunction in the KO outside the synapses in the distal end of photoreceptors where MRG4 is also localized. Differences in the phenotypes of retinal degeneration in the KO and TG models reflect a dysfunction in the two opposite ends of photoreceptors, i.e., the distal inner/outer segments and proximal synapses, respectively, indicating a second function of MRG4 in the distal photoreceptor and dual functionality of MRG4. Thus, inactivation of MRG4 by gene targeting resulted in a retinal degeneration phenotype quite different from that previously seen in the TG, attesting to the multiplicity of MRG4 function, in addition to the importance of this protein for normal retinal function. These models will be useful in elucidating the functions of HRG4/MRG4 and the mechanism of slow retinal degeneration.

Truncation mutation in HRG4 (UNC119) leads to mitochondrial ANT-1-mediated photoreceptor synaptic and retinal degeneration by apoptosis.

PURPOSE: To characterize the time course of apoptosis and degeneration in a transgenic mouse model of retinal degeneration based on truncated mutant HRG4; to investigate the nature of binding of the mutant HRG4 to its target, ADP-ribosylation factor-like (ARL)2; to study its effects on the downstream molecules Binder-of-ARL2 (BART) and adenine nucleotide transporter (ANT)-1 and on the induction of apoptosis. METHODS: Saturation binding, microscopic morphometric, Western blot, immunofluorescence, and TUNEL analyses were used. RESULTS: Increased apoptosis did not occur until 20 months in the transgenic retina, consistent with the delayed-onset degeneration in this model. The truncated HRG4 protein exhibited approximately threefold greater affinity for ARL2 than the wild-type HRG4, likely resulting in nonfunctional sequestration of ARL2. A significant decrease in ARL2 was present by 20 months, accompanied by a 50% decrease in ANT-1 in the photoreceptor synaptic mitochondria, with evidence of mitochondrial dysfunction. Preapoptotic degeneration in the photoreceptor synapse was demonstrated with cytochrome c release and caspase 3 activation within the synapse-without evidence of TUNEL-positive apoptosis in the photoreceptor cell body-indicating an initial event in the synapse leading to apoptosis. Caspase 3 was activated in the accompanying secondary neuron, consistent with transsynaptic degeneration. CONCLUSIONS: The results support a novel mechanism of retinal degeneration in which preapoptotic degeneration starts in the photoreceptor synapse because of a deficiency in ANT-1 and spreads to the secondary neuron transsynaptically, followed by apoptosis and degeneration in the cell body of the photoreceptor.