Aortic dilation and dissection are well-recognized cardiac abnormalities in 
women with Turner syndrome (TS), although the underlying pathophysiology is not 
fully understood. We report on a 46-year-old Hispanic woman who was previously 
diagnosed with moyamoya disease on magnetic resonance imaging after a 
presentation with stroke-like symptoms. Her features were consistent with TS and 
chromosome analysis revealed mosaicism in which 17% of the cells showed a 
pseudoisodicentric Y chromosome: 45,X (25)/46,X psu idic (Y)(11.2) (5). A 
preceding screening transthoracic echocardiogram had shown a bicuspid aortic 
valve (BAV) with an aortic diameter of 3.2 cm; at the time of moyamoya 
diagnosis, the aorta was 3.5 cm with mild aortic stenosis and mild aortic 
regurgitation. Four years later, the patient had had an acute aortic dissection, 
Stanford type A, which was repaired successfully. This case report is the third 
individual with TS associated with moyamoya disease and the first associated 
with dissection. The small number of cases does not allow detailed analysis 
other than noting patient age (two older than 40 years), karyotype (two others 
associated with isochrome Xq), and associated cardiac risk factors (one with 
BAV). Although this may be a chance occurrence, we hypothesize that moyamoya 
disease could be a manifestation of the vasculopathy in TS.