Differential Diagnosis for Ana 1:1280, Transient Monocular Vision Loss, CRP Normal

• Single Most Likely Diagnosis
  • Giant Cell Arteritis (GCA): This condition is a strong consideration given the high ANA titer and transient monocular vision loss. Although CRP is normal, GCA can present with a wide range of inflammatory marker levels, and vision symptoms are a key red flag.
• Other Likely Diagnoses
  • Antiphospholipid Syndrome (APS): The high ANA titer and transient monocular vision loss could suggest APS, especially if there's a history of thrombotic events or recurrent miscarriages.
  • Systemic Lupus Erythematosus (SLE): Given the high ANA titer, SLE should be considered, although the specific symptom of transient monocular vision loss is less common in SLE.
  • Vasculitis (e.g., Wegener's Granulomatosis): Although less likely, other forms of vasculitis could present with vision loss and elevated ANA, though typically other symptoms and abnormal CRP would be expected.
• Do Not Miss Diagnoses
  • Central Retinal Artery Occlusion: This is an ocular emergency that can cause sudden, painless monocular vision loss. It's crucial to rule out this condition promptly due to its potential for irreversible vision loss if not treated immediately.
  • Carotid Artery Dissection or Stenosis: These conditions can cause transient monocular vision loss (amaurosis fugax) and are critical to diagnose due to their association with stroke risk.
• Rare Diagnoses
  • Susac Syndrome: A rare condition characterized by microangiopathy of the retina, brain, and inner ear, which could explain the vision loss but would be unusual given the high ANA titer without other typical symptoms.
  • Eales Disease: A rare idiopathic condition causing retinal vasculitis and vision loss, typically in young adults, but the high ANA titer would be an atypical finding.