Genetic factors play an important role in the study of the pathogenesis of smog. We performed vascular screening with transcranial Doppler ultrasound (TCD) for immediate family members with disseminated smog from 2011 to 2013. A total of 285 family members of smog patients were screened, and 21 smog patients were detected. This is the largest group of case screening studies for patients with disseminated smog. The results of the study confirm that familial smog may account for a much higher proportion of the total number of patients than previously expected. Some family members of patients with disseminated smog also have smog, but it is not detected because they are asymptomatic or have mild symptoms. Therefore, regular screening of family members of patients with smog may help to improve the detection rate of such patients. TCD may be the preferred method for screening such patients because it is noninvasive and inexpensive. Therefore, we suggest that family members of patients with smog should be screened regularly for TCD and should visit the hospital as soon as possible if they develop ischemic symptoms such as limb weakness, slurred speech, and blurred vision.