Abstract
Purpose
To report on a case of diffuse unilateral subacute neuroretinitis (DUSN) that was successfully treated with a short course of oral albendazole.
Observations
A 51-year-old male presented with severe visual loss secondary to DUSN associated with a positive Toxocara serology. Because the parasite could not be detected on fundoscopy, first-line treatment with photocoagulation could not be administered. Treatment with a 6-day course of oral albendazole resulted in the resolution of DUSN as well as the restoration of visual acuity.
Conclusion and importance
Although DUSN is characterized by the presence of a parasitic organism in the retina, there are cases in which the parasite is not visible. Albendazole has been used to treat such cases, but a standard treatment regimen has not been determined yet. Our case suggests that the resolution of DUSN can be achieved with short-term albendazole therapy.
1
Introduction
Diffuse unilateral subacute neuroretinitis (DUSN) is an infectious ocular disease that may result in visual-acuity deterioration. Although this disease’s pathogenesis remains unclear and a specific causative agent has not been identified, parasitic organisms such as Baylisascaris procyonis, Ancylostoma caninum, and Toxocara canis are thought to be involved in its etiology. , DUSN is more prevalent in young individuals, and most patients present with unilateral disease. , In the early stages of DUSN, patients may present with a mild loss of visual acuity associated with vitritis, optic disc edema, and gray-white retinal lesions. Because symptoms tend to be more subtle during the early stages, patients may seek medical care later in the course of the disease. Late-stage DUSN is characterized by a severe loss of visual acuity, degenerative retinal pigment epithelium changes, optic atrophy, and retinal arteriole narrowing. ,
DUSN is confirmed when a parasite is identified in the retina of a patient presenting with the disease’s classic signs and symptoms. , However, in many cases, the parasite cannot be identified, making the diagnosis (in those cases) of DUSN a challenge. , Maintaining a high index of suspicion for this condition is crucial, as early detection and treatment have been associated with better patient outcomes. ,
When the parasite is visualized, the first-line treatment of DUSN consists of laser photocoagulation. , In cases in which the parasite cannot be detected, albendazole has proven to be a valuable second option. , However, there is no consensus about the specific regimen that should be used to treat DUSN. In this report, we present the case of a 51-year-old male with DUSN that was associated with a positive Toxocara serology. Treatment with a 6-day course of albendazole resulted in the resolution of the neuroretinitis and significant improvement in visual acuity.
2
Case report
A 51-year-old Hispanic male reported a 3-week history of constant, severe blurred vision of the right eye. He had been referred to a retina and uveitis specialist for evaluation of his retinal lesions and cystoid macular edema of the right eye. His primary ophthalmologist had also noted fine keratic precipitates, vitreous cells, and foci of retinitis in the patient’s right eye and had started him on prednisolone acetate 1%, every 2 hours, and ketorolac 0.5%, four times daily, five days before presentation. The review of systems was negative. The patient’s past ocular history revealed that he had bilateral cataracts, and his past medical history was remarkable for untreated hypercholesterolemia. The patient denied using alcohol, tobacco, or illicit drug use as well as having traveled outside Puerto Rico. He had a pet dog and a rabbit.
A comprehensive ophthalmological exam revealed a best-corrected visual acuity of finger counting in the right eye and 20/40 in the left eye; the patient’s manifest refractions were +0.50–0.50 × 180 (right eye) and +1.50–0.50 × 180 (left eye). His intraocular pressure was 15 mmHg for both eyes. Confrontational visual fields testing revealed a nasal defect in the right eye; visual fields were full in the left eye. Amsler grid testing revealed a central scotoma in the right eye and no abnormalities in the left. The patient’s pupils were round and reactive to light, and there was no afferent pupillary defect. His extraocular movements were intact, and the orbits were within normal limits. A slit lamp exam revealed +2 nuclear sclerosis in both eyes but no keratic precipitates, posterior synechiae, or anterior chamber cells in either eye. The vitreous in the right eye had 1+ cells and was clear in the left.
An examination of the right fundus revealed subtle disc edema and an area of retinitis measuring approximately four discs in diameter adjacent to the inferior border of the disc. This area of retinitis had associated exudation with precipitation of hard exudate, inferonasally and within the macula in a star pattern. Additionally, a chorioretinal scar, measuring approximately one disc diameter, was noted approximately 4500 μm superotemporal to the fovea ( Fig. 1 A). Macular spectral-domain optical coherence tomography (SD-OCT) revealed cystoid intraretinal and sub-foveal fluid.
A presumptive diagnosis of neuroretinitis in the right eye was made, and a workup to rule out such infectious causes as syphilis, toxoplasmosis , bartonellosis , and tuberculosis was ordered. Empiric treatment with prednisolone acetate 1% and broad-spectrum antibiotics, including doxycycline (100mg twice daily) and trimethoprim/sulfamethoxazole (SMZ-TMP) (800/160 four times daily), was initiated. Lactobacillus acidophilus (175mg daily) was also prescribed.
One week after the presentation, his visual acuity had improved to 20/200 in the right eye and remained unchanged in the left eye. The right fundus examination revealed persistent foci of retinitis and macular exudates. The macular SD-OCT showed an improvement of the macular edema, though persistent subfoveal fluid was detected. The initial workup, including a fluorescent treponemal antibody absorption test, a rapid plasma reagin test; Bartonella henselae, Bartonella quintana, and Toxoplasma antibody (IgG and IgM) panels; an HIV-1 and -2 test; and a Mantoux skin test, was negative. The chest X-ray revealed a minimally elongated and calcified aorta, was otherwise within normal limits. A CBC revealed an elevated WBC (10.5 × 10 3 ) with a normal differential (5% eosinophils). A comprehensive metabolic panel revealed a slight increase in the albumin/globulin ratio of 1.83, which was otherwise within normal limits.
On the two-week follow-up exam, there were no changes in visual acuity; however, the OCT revealed the complete resolution of the edema. A further workup, which included a test for Toxocara antibodies and an examination of a stool sample for ova and parasites, was ordered. After three weeks, the uncorrected visual acuity had improved to 20/100 in the right eye. At this visit, the patient reported a four-day history of fever, headache, and sore throat. He was evaluated in the emergency room and found to have neck lymphadenopathy. A CT scan with contrast enhancement of the neck revealed necrotic lymph nodes with stranding and potential extra-capsular spread. The emergency room physician added oral amoxicillin to the patient’s drug regimen. The following day, the patient was evaluated by an otorhinolaryngologist, who found no lesions on performing a flexible laryngoscopy. A neck biopsy and follow-up evaluation were scheduled for two weeks hence, and the amoxicillin was discontinued.
At the four-week follow-up visit, the findings for the right eye remained unchanged, but a white retinal lesion, measuring approximately 750 μm in diameter, was noted along the inferotemporal arcade of the left eye. The lesion was thought to represent a new focus of retinitis ( Fig. 2 A). The patient’s stool was negative for ova and parasites. However, Toxocara (total antibody) testing by ELISA was positive. Following this test, ophthalmic images from the referring physician were sought and reviewed. Obtained one week before the retina and uveitis specialist evaluated the patient, these images revealed a curved roundworm, measuring approximately 1000 μm and surrounded by patches of retinitis that were located in the superotemporal region, correlating to where the chorioretinal scar was noted on the patient’s initial evaluation ( Fig. 1 B). The parasite was not visible on the fundus images obtained in subsequent visits.
