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Acute Macular Neuroretinopathy (AMN): Rare Outer Retinal Disorder

Sudden Paracentral Scotoma in Young Adults

AMN is a rare outer retinal disorder affecting young adults (20–40s, F>M). Sudden paracentral scotoma(s) arise from infarcts at the level of the deep capillary plexus / outer nuclear layer.

Clinical Features

  • Sudden onset: paracentral scotoma, blurred vision, metamorphopsia.
  • Often unilateral (70%), can be bilateral (sequential or simultaneous).
  • Associated: viral prodrome, flu-like illness, oral contraceptives, autoimmune, vascular dysregulation.

Diagnostic Imaging (Hallmark Findings)

  • OCT: Hyperreflective band at outer nuclear layer / ellipsoid zone (day 1–3); later: EZ disruption, ONL thinning.
  • Infrared (IR) / Fundus Autofluorescence: Petaloid, wedge-shaped lesions pointing to fovea — visible before fundus changes.
  • Fluorescein Angiography: Usually normal (choriocapillaris perfusion intact) — distinguishes from MEWDS, PIC.
  • OCT-A: Flow voids in deep capillary plexus / choriocapillaris.

Differential Diagnosis

ConditionDistinguishing Features
MEWDSYoung F, viral prodrome, granular foveal changes, FA: hyperfluorescent dots, self-limited
AZOORBilateral, photopsias, enlarged blind spot, FA: window defects
PIC / MCPChorioretinal scars, FA: early hyperfluorescence, late staining
AZOOR complexOverlapping spectrum; AMN = paracentral acute middle maculopathy (PAMM) counterpart

Etiology (Hypothesized)

  • Microvascular occlusion (deep capillary plexus) — vasospasm, hypercoagulability, endothelial dysfunction.
  • Associations: OCPs, pregnancy, migraine, autoimmune (SLE, APS), vaccination (rare).
  • Genetic: some familial clusters.

Management

  • No proven disease-modifying treatment.
  • Observation — most stabilize/improve over months.
  • Empiric: aspirin, anticoagulation if hypercoagulable workup positive.
  • Corticosteroids / immunosuppressives — anecdotal; not standard.
  • Treat associated systemic condition.

Outcomes

  • Visual acuity: often returns to 20/20–20/40.
  • Scotomas: may persist (absolute or relative).
  • Recurrence: 10–20% (same or fellow eye).
  • Long-term: EZ disruption on OCT correlates with persistent scotoma.

Related Entity: PAMM

Paracentral Acute Middle Maculopathy — similar demographics, lesions at INL level (hyperreflective band on OCT). Often coexists with AMN. Same vascular pathophysiology.

Bottom Line

AMN = sudden paracentral scotoma in young adult + characteristic OCT/IR lesions. Benign course typical. Rule out mimics. Monitor for recurrence. Refer for hypercoagulable workup if indicated.

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