Neurodevelopmental abnormalities in autism spectrum disorders (ASD) have yet to be reliably identified. Recent work suggests that a likely roadblock is the high degree of subject-specific variation in ASD. We previously implemented a validated network analysis method that identified an atypical functional network underlying individual differences in ASD symptom severity. Here we applied the same approach cross-modally to investigate the association between intra-pair differences in structural connectivity networks and within-twin-pair differences in ASD symptom severity in monozygotic twins. A single structural subnetwork was identified with similar hubs implicating the salience and face-perception networks in severity of social deficits in ASD.