Molecular approaches in the diagnosis of primary immunodeficiency diseases

Over 120 inherited primary immunodeficiency diseases (PIDs) are known to exist. The genes responsible for many of these diseases have also been identified. Recent advances in diagnostic procedures have enabled these to be identified earlier and appropriately treated. While a number of approaches are available to identify mutations, direct sequencing remains the gold standard. This approach identifies the exact genetic change with substantial precision. We suggest that a sensitive and economical approach to mutation detection could be the direct sequencing of cDNA followed by the confirmatory sequencing of the corresponding exon. While screening techniques such as single-stranded conformation polymorphism (SSCP), heteroduplex analysis (HA), denaturing gradient gel electrophoresis (DGGE), and denaturing high-performance liquid chromatography (dHPLC) have proven useful, each has inherent advantages and disadvantages. We discuss these advantages and disadvantages and also discuss the potential of future sequencing technologies such as pyrosequencing, combinatorial sequencing-by-hybridization, multiplex polymerase colony (polony), and resequencing arrays as tools for future mutation detection. In addition we briefly discuss several high-throughput SNP detection technologies.