Annual Incidence and Prevalence
- 0.54 to 0.94 per 100,000 per year in Japan: The annual incidence and prevalence were reported as 0.54 – 0.94 / 100,000 and 6.03 – 10.5 / 100,000, respectively in Japan (2,34).
- 50.7 per 100,000 prevalence in Japan: If asymptomatic patients diagnosed incidentally were included, the prevalence goes up to 50.7 / 100,000 in Japan (20).
- Bimodal distribution with greatest at 5-9 years: There are two peaks, one at the age of 5-9 years and the other smaller one, at the age around 40 (48).
- Females more than males: Moyamoya Disease occurs more frequently in females in most populations with the M;F ratio 1:1.6 – 2.18 (2,34,49,61).
- Particularly prevalent in Asians: Although prevalent throughout the world, Moyamoya Disease occurs more frequently in Asians, especially in Far Eastern Asians. In the United States it is reported that African Americans are affected at a higher prevalence than whites or Hispanics (59).
- Family history: Positive family history is a strong risk factor. The incidence in siblings and offspring of probands are about 3% and 2.4%, respectively, 42 and 34 times higher than general population, although this may be lower in North American populations (14,30).
Relationships to Other Disease States and Syndromes
By definition, Moyamoya Disease should not accompany other underlying diseases or conditions. However, the below listed conditions can give rise to a quasi Moyamoya Disease state and they can be a window into the basic pathophysiologic mechanism of of it.
- Neurofibromatosis Type I
- Down Syndrome/Trisomy 21
- Sickle cell anemia
- Following cranial irradiation
- Brain tumor
- Systemic arterial narrowing/mid-aortic syndrome with renal artery stenosis