Low-level mosaicism in tuberous sclerosis complex: prevalence, clinical features, and risk of disease transmission

Krinio Giannikou, Kathryn D. Lasseter, Joannes M. Grevelink, Magdalena E. Tyburczy, Kira A. Dies, Zachary Zhu, Lana Hamieh, Bruce M. Wollison, Aaron R. Thorner, Stephen J. Ruoss, Elizabeth A. Thiele, Mustafa Sahin, David J. Kwiatkowski

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Purpose: To examine the prevalence and spectrum of mosaic variant allele frequency (MVAF) in tuberous sclerosis complex (TSC) patients with low-level mosaicism and correlate genetic findings with clinical features and transmission risk. Methods: Massively parallel sequencing was performed on 39 mosaic TSC patients with 170 different tissue samples. Results: TSC mosaic patients (MVAF: 0–10%, median 1.7% in blood DNA) had a milder and distinct clinical phenotype in comparison with other TSC series, with similar facial angiofibromas (92%) and kidney angiomyolipomas (83%), and fewer seizures, cortical tubers, and multiple other manifestations (p < 0.0001 for six features). MVAF of TSC1/TSC2 pathogenic variants was highly variable in different tissue samples. Remarkably, skin lesions were the most reliable tissue for variant identification, and 6 of 39 (15%) patients showed no evidence of the variant in blood. Semen analysis showed absence of the variant in 3 of 5 mosaic men. The expected distribution of MVAF in comparison with that observed here suggests that there is a considerable number of individuals with low-level mosaicism for a TSC2 pathogenic variant who are not recognized clinically. Conclusion: Our findings provide information on variability in MVAF and risk of transmission that has broad implications for other mosaic genetic disorders.

Original languageEnglish
Pages (from-to)2639-2643
Number of pages5
JournalGenetics in Medicine
Issue number11
StatePublished - Nov 1 2019


  • TSC1
  • TSC2
  • mosaicism
  • transmission risk
  • tuberous sclerosis complex


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