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. Author manuscript; available in PMC: 2019 May 29.
Published in final edited form as: Am J Med Genet C Semin Med Genet. 2018 Dec;178(4):432–439. doi: 10.1002/ajmg.c.31666

Table IV.

Alternative hypotheses not addressed by current genomic investigations

Feature Rationale for failure
Postzygotic mutation Alternate allele present at low levels or absent from blood and/or saliva
Variants not detected by exome sequencing Non-coding DNA variants
Complex structural rearrangements
Genetic heterogeneity Small sample size
Incomplete penetrance, variable expressivity, and non-Mendelian inheritance Small sample size
Epigenetic causes Not due to DNA variants