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Woman presents with acute onset of unilateral blurred vision
Dilated fundus exam showed disc edema with subretinal fluid in the right eye.
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A 57-year-old woman was evaluated 1 day after the acute onset of blurred vision characterized as “dark clouds” in her right eye. She denied pain or other associated ocular symptoms. She had been experiencing fatigue and chills for 1 month before the onset of her visual symptoms.
Her ocular history was significant for blunt trauma to the left eye, resulting in anisocoria. She had Lyme arthritis 4 years previously, treated with 1 month of intravenous antibiotics. She owned 13 cats that scratched her frequently, the most recent of which was 2 months before presentation.
Examination
On examination, the patient’s best corrected visual acuity was 20/200 in the right eye and 20/20 in the left eye. Her pupils were round and reactive, although the left was 1 mm larger than the right. There was no afferent pupillary defect, although she did note 20% color desaturation in the right eye. She missed two AOHRR color plates in the right eye. IOPs and anterior segment examination were normal without anterior chamber inflammation.
Dilated fundus exam was remarkable for disc edema and subretinal fluid in the right eye without evidence of vitreous inflammation (Figure 1). Automated visual fields demonstrated a paracentral scotoma and enlarged blind spot in the right eye and a full field in the left eye (Figure 2). Optical coherence tomography showed both subretinal and intraretinal fluid in the right eye (Figure 3). On fundus fluorescein angiography, there was leakage of the disc in the right eye without any areas of retinal leakage identified (Figure 4).
Figure 1. Color fundus photos revealing unilateral disc edema and subretinal fluid in the right eye.
Images: Muakkassa N, Hedges TR
Figure 2. 30-2 Humphrey visual fields showing a paracentral scotoma and enlarged blind spot in the right eye.
Figure 3. OCT image of the right eye revealing subretinal and intraretinal fluid and a swollen optic nerve.
Figure 4. Fundus fluorescein angiogram of the right eye revealing disc leakage with normal retinal and choroidal filling.
What is your diagnosis?
Loss of vision, optic disc edema
The differential diagnosis for this patient with unilateral central loss of vision and optic disc edema includes inflammatory, infectious, vascular or neoplastic causes.
Inflammatory causes include systemic lupus erythematosus, polyarteritis nodosa, sarcoidosis and demyelinating disease. Systemic lupus erythematosus and polyarteritis nodosa may present with steroid-responsive optic neuritis, but both are quite rare. Sarcoidosis can cause papillitis, optic disc edema secondary to adjacent retinitis or papilledema resulting from intracranial lesions. Demyelinating disease causing an anterior optic neuritis should be considered in our patient, but it is unlikely given the presence of flame hemorrhages.
Infectious etiologies of unilateral disc edema include syphilis, Lyme disease, Bartonella henselae neuroretinitis (cat scratch disease), tuberculosis or parainfectious optic neuritis. Syphilis, tuberculosis and Lyme disease have wide varieties of presentations, and serologic testing should be performed to aid in making the diagnosis. The classic presentation of B. henselae neuroretinitis is unilateral disc edema with a macular star. Neuroretinitis should be considered highly on the differential given the patient’s history of multiple cat scratches and recent flu-like illness. Parainfectious optic neuritis should also be considered given her recent flu-like illness.
Vascular causes to consider include ischemic optic neuropathy, papillophlebitis, diabetic papillopathy, central retinal vein occlusion or radiation retinopathy. Radiation retinopathy and diabetic papillopathy were eliminated from the differential in our patient because she did not have a history of either. We also eliminated papillophlebitis and central retinal vein occlusion given the lack of venous tortuosity. The most likely of these in our patient was non-arteritic anterior ischemic optic neuropathy (NAION), which typically presents with unilateral disc edema and flame hemorrhages.
Neoplastic causes, such as leukemia, lymphoma, compression by tumor and optic nerve metastasis, must be considered as well.
Diagnosis and management
A systemic work-up was ordered to evaluate for the various pathologies listed above. Blood work revealed a positive Lyme IgG and Lyme C6 peptide ELISA, but Lyme IgM titers were negative. In cases of late manifestations of Lyme disease, Lyme IgG and Lyme C6 titers may remain positive even after adequate treatment. Additionally, reinfection is very uncommon in patients with late manifestations of Lyme disease, which is thought to be due to persistent immunity. Therefore, despite these test results, this presentation was very unlikely to be active Lyme disease given our patient’s history of adequately treated Lyme arthritis.
Testing for cat scratch disease revealed positive titers for B. henselae IgG but negative IgM titers. The sensitivity of IgM testing is relatively low, with one study reporting a sensitivity of 45% and a specificity of 98%. Additionally, IgM titers may become negative as soon as 3 months after the initial inoculation and may be missed if the patient presents outside this short window. Therefore, a negative IgM titer does not rule out an acute infection.
NAION classically presents with unilateral disc edema, flame hemorrhages and an altitudinal field defect on visual field testing. Subretinal fluid tracking from the disc to the macula has been well described in cases of NAION. However, the absence of systemic risk factors, such as diabetes, hypertension or hyperlipidemia, and a “disc at risk” makes this diagnosis less likely in our patient.
Serologic testing was negative for syphilis, autoimmune disease and tuberculosis. A complete blood count was normal, making leukemia and lymphoma unlikely. After this systemic work-up, the leading diagnosis was B. henselae neuroretinitis.
OCT performed 1 week after initial presentation showed new evidence of intraretinal and subretinal exudates with persistent fluid (Figure 5). Three days later, a macular star was seen on funduscopic examination. The patient was started on doxycycline and prednisone for presumed cat scratch disease. Two months after her initial presentation, her visual acuity improved to 20/40 eccentrically. Color fundus photographs taken at that visit showed a complete macular star, and OCT imaging showed intraretinal exudates with complete resolution of intraretinal and subretinal fluid (Figure 6).
Figure 5. OCT image at 1 week showing subretinal and intraretinal fluid and exudates.
Figure 6. Color fundus photos 2 months after presentation showing a complete macular star (a). Correlating OCT image showing resolution of subretinal and intraretinal fluid with persistent intraretinal exudates and disruption of the subfoveal external limiting membrane and IS/OS junction (b).
Discussion
B. henselae neuroretinitis occurs in 1% to 2% of patients with cat scratch disease. Inoculation occurs after exposure to infected cats or fleas. Symptoms of systemic infection, or cat scratch disease, include a flu-like illness with fevers and lymphadenopathy. Cutaneous bacillary angiomatosis and liver or spleen involvement can also occur. Other ocular findings associated with B. henselae infection include Parinaud’s oculoglandular syndrome, focal retinochoroiditis, or retinal vasculitis with subsequent arterial or venous occlusions. B. henselae neuroretinitis presents most commonly in children and young adults. It is usually unilateral, and ocular symptoms occur within 1 month of the onset of systemic symptoms. The disease is classified by an optic neuropathy with disc edema and a partial or complete macular star. There is typically anterior or vitreal inflammation, and retinochoroiditis may be present. A peripapillary serous retinal detachment may be found early in the disease. A macular star typically is found 2 to 4 weeks after the onset of ocular symptoms, although some patients never form a macular star.
B. henselae neuroretinitis is a self-limited disease, and the need for treatment is controversial. Treated immunocompromised patients have shown significant improvement; however, there are no randomized studies to support treating immunocompetent patients. Severe disease can be treated with doxycycline with or without rifampin for 2 to 4 weeks.