Moyamoya syndrome

Moyamoya syndrome, also termed the moyamoya pattern or phenomenon, is due to numerous conditions that can cause arterial occlusion of the circle of Willis, with resultant collaterals, and appearances reminiscent of moyamoya disease. These conditions include ^1-4 :

• vessel wall abnormalities
  • atherosclerosis ⁵
  • radiation induced vasculopathy
  • fibromuscular dysplasia
  • Marfan syndrome
  • Ehlers-Danlos syndrome
• phakomatoses
  • neurofibromatosis type 1(NF1)
  • tuberous sclerosis (TS)
• connective tissue disorders
  • systemic lupus erythematosus (SLE)
  • antiphospholipid syndrome
• blood dyscrasias 
  • sickle cell disease
  • essential thrombocytopenia ⁶
  • polycythemia rubra vera ^7,8
  • aplastic anemia
  • Fanconi anemia​
• infection
  • tuberculous meningitis
  • bacterial meningitis
  • post-varicella vasculitis
  • leptospirosis
• less common causes
  • Graves disease ⁵
  • Down syndrome
  • ulcerative colitis (UC)
  • Apert syndrome
  • oral contraceptive use