Case Report

An 18-year-old Caucasian female presented to the Bascom Palmer Emergency Department due to new onset of paracentral scotomas and floaters in both eyes for the past 10 days. Upon review of systems questioning, the patient had a recent febrile illness following a trip to the Bahamas. She developed a disseminated erythematous rash on her arms and legs, hemoptysis, shortness of breath, and pelvic cramping/bleeding. She had no significant medical or ocular history. She was taking norethindrone-ethinyl estradiol (oral contraceptive pills) and diphenhydramine. She was also on dexamethasone and trimethoprim/sulfamethoxazole, prescribed by an outside provider due to her systemic symptoms.  

Best corrected visual acuity was 20/20 OD and 20/20 OS. All other preliminary testing was normal. Dilated fundus exam showed multifocal alterations in macular pigment OU (Figure 1). Additional imaging was ordered including OCT macula, near-infrared imaging (NIR) and fundus autofluorescence (FAF). The macular OCT showed multifocal areas of photoreceptor and outer retinal atrophy, choroidal thickening without fluid, and foci of outer retinal hyperreflectivity (Figure 4). NIR imaging demonstrated multifocal paracentral hyporeflectant lesions OU (Figure 2). Fundus autofluorescence (FAF) showed multifocal paracentral faintly hyperautofluorescent lesions OU (Figure 3). 

A thorough systemic workup was initiated due to the unique ophthalmic presentation in the setting of numerous positive review of system findings. Labs were ordered including CBC with diff, CMP, ACE, FTA-ABS, lysozyme, RPR, West Nile, Chikungunya, Zika, Dengue. Results were all normal with the exception of elevated transaminases which subsequently improved. An ultrasound of the liver and pelvis was ordered which was unremarkable. Lastly, a chest X-ray was ordered which showed peribronchial thickening. 

Based on the patient’s symptoms and temporal association with illness, combined with the clinical picture, the patient was diagnosed with Acute Macular Neuroretinopathy (AMN). She was instructed to complete medications as directed by an outside provider and return in 2-3 weeks to monitor. At follow-up, she reported her floaters/scotomas were stable and persistent. Clinical findings and ancillary testing were also stable. 

FIG 1: Fundus photos – multifocal alterations in macular pigment OU 

FIG 2: Near-infrared imaging (NIR) – multifocal paracentral hyporeflectant lesions OU

FIG 3: Fundus autofluorescence – multifocal paracentral faintly hyperautofluorescent lesions OU

FIG 4: OCT – multifocal photoreceptor, outer plexiform (OPL) and outer nuclear (ONL) layer atrophy with choroidal thickening OU

Discussion

AMN is a rare condition typically affecting young women. Though the pathophysiology is unclear, it is thought to be due to microvascular ischemia at the level of the deep outer retinal capillary network.1,2 As in our patient, ophthalmic symptoms are often preceded by a viral-like prodrome, which can be exacerbated by oral contraceptive use. Other risk factors include systemic illness (E.g., dengue fever), sympathomimetics, trauma, hypovolemia, and dehydration.2 Diagnosis is clinical, and AMN characteristically produces reddish-brown petaloid lesions that are generally pointed toward the fovea. OCT and NIR are most useful in identifying this disease. Acutely, the lesions present as thickening and hyper-reflectivity of the ONL and OPL, and chronically these lesions progress to atrophy of the ONL and underlying photoreceptors.4 Accordingly, these lesions appear hyporeflectant on NIR imaging.

Visual scotomas often persist in patients with AMN, however central visual acuity is generally preserved. There is no standard treatment for AMN, however some research shows corticosteroids may improve choroidal perfusion and subsequent outer-retinal perfusion.2,5 Since our patient already presented on oral dexamethasone for her systemic symptoms, additional or prolonged corticosteroid therapy was deferred.

Conclusion

Acute Macular Neuroretinopathy can be diagnosed clinically due to the highly characteristic presentation of petaloid macular lesions that are best seen on OCT and NIR imaging. History aids in diagnosis, as the majority of AMN patients have a viral-like prodrome, and risk factors such as oral contraceptive use. It’s important to understand that treatment for AMN is not currently recommended due to the likely ischemic and irreversible nature, but further research on the pathophysiology is warranted.

Credit: Rami Aboumourad, OD, FAAO

References

  1. Bhavsar KV, Lin S, Rahimy E, et al. Acute macular neuroretinopathy: A comprehensive review of the literature. Survey of Ophthalmology. 2016;61(5):538-565. doi:10.1016/j.survophthal.2016.03.003
  2. Hsieh MC, Chen SN. Improvement of deep capillary and choroidal blood void in optical coherence tomography angiography in a case of acute macular neuroretinopathy after prednisolone treatment. Journal of the Formosan Medical Association. 2020;119(10):1550-1554. doi:10.1016/j.jfma.2020.03.023
  3. Iovino C, Au A, Ramtohul P, et al. Coincident PAMM and AMN and Insights Into a Common Pathophysiology. American Journal of Ophthalmology. 2022;236:136-146. doi:10.1016/j.ajo.2021.07.004
  4. Fawzi AA, Pappuru RR, Sarraf D, et al. ACUTE MACULAR NEURORETINOPATHY: Long-Term Insights Revealed by Multimodal Imaging. RETINA. 2012;32(8):1500. doi:10.1097/IAE.0b013e318263d0c3
  5. Oliver JC, DePoe SA. Case Report: Recurrent Acute Macular Neuroretinopathy—Monitoring Recovery with Multimodal Imaging. Optometry and Vision Science. 2023;100(3):232. doi:10.1097/OPX.0000000000001993