A 55-year-old elderly patient presented with unilateral blindness, unilateral headache lasting for 2 months and shows increased ESR. The diagnosis is

(A) Giant cell arteritis # Giant-cell arteritis (GCA or Temporal arteritis or Cranial arteritis) or Horton disease is an inflammatory disease of blood vessels most commonly involving large and medium arteries of the head. It is a form of vasculitis. Patients present with: bruits; fever; headache; tenderness and sensitivity on the scalp; jaw claudication (pain in jaw when chewing); tongue claudication (pain in tongue when chewing) and necrosis; reduced visual acuity (blurred vision); acute visual loss (sudden blindness); diplopia (double vision); acute tinnitus (ringing in the ears). The inflammation may affect blood supply to the eye and blurred vision or sudden blindness may occur. In 76% of cases involving the eye, the ophthalmic artery is involved causing arteritic anterior ischemic optic neuropathy. Loss of vision in both eyes may occur very abruptly and this disease is therefore a medical emergency. Laboratory tests: LFTs, liver function tests, are abnormal particularly raised ALP- alkaline phosphatase> Erythrocyte sedimentation rate, an inflammatory marker, >60 mm/hour (normal 10-40 mm/hour), but may be normal in approximately 20% of cases.> C-reactive protein, another inflammatory marker, is also commonly elevated.> Platelets may also be elevated. Biopsy: The gold standard for diagnosing temporal arteritis is biopsy, which involves removing a small part of the vessel and examining it microscopically for giant cells infiltrating the tissue. Treatment: Corticosteroids, typically high-dose prednisone (40-60 mg. once daily), must be started as soon as the diagnosis is suspected (even before the diagnosis is confirmed by biopsy) to prevent irreversible blindness secondary to ophthalmic artery occlusion.