Acute Macular Neuroretinopathy Associated With COVID-19 Infection: Is Double Heterozygous Methylenetetrahydrofolate Reductase (MTHFR) Mutation an Underlying Risk Factor?

The goal of this report is to present a case of coronavirus disease 2019 (COVID-19)-associated acute macular neuroretinopathy (AMN) with an underlying MTHFR mutation. A 36-year-old male presented to the emergency department with a sudden-onset paracentral scotoma in his left eye. Although optical coherence tomography (OCT) was normal initially, four days later, it revealed a hyperreflective band in the outer plexiform layer with disruption of the ellipsoid zone/interdigitation zone. On infrared imaging and en-face OCT, wedge-shaped lesions were detected around the fovea with their tip oriented toward the fovea. OCT angiography, fundus autofluorescence, fundus fluorescein angiography, and visual fields were performed. The patient was positive for COVID-19 infection. The absence of medical history and the negative results of blood tests led to a diagnosis of AMN associated with COVID-19. Genetic testing for coagulation disorders was scheduled and revealed a heterozygous mutation for MTHFR C677T and A1298C. This is the first case of AMN in a patient with COVID-19 infection and a double heterozygous mutation of the MTHFR gene. Infection is the most commonly reported association of AMN, while MTHFR mutation may represent an additional underlying risk factor. Microthrombosis and small-vessel occlusion are thought to be involved in the pathophysiology of AMN, and patients should be tested for COVID-19 because it may be the first manifestation of the infection.