What is the role of mutational analysis in the workup of severe combined immunodeficiency (SCID)?

Updated: Apr 28, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Harumi Jyonouchi, MD  more...
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Answer

The techniques for mutational analysis include screening by single-strand conformation polymorphism (SSCP), which detects about 85% of mutations, and dideoxy fingerprinting (ddF), a more sensitive test. The criterion standard to detect the exact DNA change is determination of genomic DNA; direct DNA sequencing must be carried out for some molecular defects, such as those at the 3’ and 5’ ends of exons and where the full exon-intron structure of the gene has not been delineated.

When the exact mutation cannot be found, linkage analysis and restriction fragment length polymorphism (RFLP) studies may be performed within families. With the advent of specific mutation analysis, these options are needed less frequently.

Polymorphisms in the androgen receptor are used to define nonrandom inactivation of the X chromosome in the mother and other female relatives in families in which an infant boy has SCID but no extended family pedigree is informative.


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