Mosaic Carrier Test

Mosaic Carrier Test: Targeted Testing to Evaluate for Mosaicism for a Known Familial Variant

Test Requisition Form Mosaic Carrier Test Gene List



GeneDx offers targeted testing to evaluate for mosaicism for a familial variant previously identified in an individual or in a relative. Mosaic carrier analysis could be considered in the following scenarios:

  • Testing parent(s) to clarify future reproductive risks when a variant was identified in a child
  • Testing a parent who is suspected to be mosaic due to a mild clinical presentation or the presence of only certain tissue-specific features of the disorder
  • Testing additional tissue samples to evaluate for the possibility of tissue-specific mosaicism in a proband
  • CLIA confirmation of suspected mosaic findings identified by a research study

Mosaic carrier analysis is available for most variants in genes on the GeneDx testing menu. In many cases, mosaic carrier analysis is also available for individuals who had variants identified by testing at an outside laboratory or as part of a research study. If the family has not had prior testing at GeneDx, please see the table below for the specific requirements. At this time, mosaic carrier analysis is not available for copy number variants (CNVs). Additionally, there are some genes or portions of genes are not amenable to mosaic carrier analysis for sequencing variants. If prior trio testing was performed including the patient and both parents as part of exome or genome sequencing, an Xpanded panel, or another testing scenario, please contact GeneDx in advance of sample submission to discuss the utility of mosaic carrier analysis.

Scenarios when mosaic carrier analysis could be considered:

Sample from Proband as Positive Control

Copy of Report from Outside Laboratory

Preferred Sample Type

1. Evaluate for parental mosaicism when proband not tested or tested by Sanger sequencing: Parents not tested or tested by Sanger sequencing. Not Necessary Not Necessary Blood
Buccal swab
2. Evaluate for parental mosaicism when proband tested by research study or at outside lab: Parents not tested or tested by Sanger Sequencing Required Required Blood
Buccal Swab
3. Evaluate for mosaicism in an affected parent: Parent had prior testing as part of trio testing for proband that was negative for the variant. Not necessary if prior testing done at GeneDx. Required if done at an outside laboratory. Not necessary if prior testing done at GeneDx. Required if done at an outside laboratory. Affected tissue if possible. if not possible to send affected tissue, please call to discuss.
4. Evaluate for parental mosaicism when there are multiple affected children: Parent had prior testing as part of trio testing for proband that was negative for the variant. Not necessary if prior testing done at GeneDx. Required if done at an outside laboratory. Not necessary if prior testing done at GeneDx. Required if done at an outside laboratory. Please call in advance to discuss.
5. Evaluate for suspected mosaicism in proband previously reported to be heterozygous for variant: Proband reported to be heterozygous for variant by prior testing, but clinical features suggest possible mosaicism. Not necessary if prior testing done at GeneDx. Required if done at an outside laboratory. Not necessary if prior testing done at GeneDx. Required if done at an outside laboratory. Please call in advance to discuss.
6. Evaluate proband to differentiate acquired or somatic mosaicism from constitutional variant: Proband is heterozygous or mosaic for variant in DNA extracted from blood. Not necessary if prior testing done at GeneDx. Required if done at an outside laboratory. Not necessary if prior testing done at GeneDx. Required if done at an outside laboratory. Fibroblasts recommended.


To order mosaic carrier analysis, please use this requisition form, and provide the requested information:

  1. The name of the gene
  2. The specific variant for mosaic carrier analysis
  3. If the proband or a relative was previously tested at GeneDx, provide the GeneDx accession number and/or the full name of the relative

Please see our standard Specimen Requirements page for information about obtaining and shipping samples. The requisition form MUST accompany the sample or testing may be cancelled or delayed.