Mutation Screening by Denaturing Gradient Gel Electrophoresis in North American Patients with Acute Intermittent Porphyria (Technical Briefs‪)‬

Acute intermittent porphyria (AIP) is a dominantly inherited disorder of heme metabolism caused by a 50% decrease in the activity of porphobilinogen deaminase (EC 4.3.1.8.). The estimated prevalence of the disease is 1:1000 to 1.5:100 000, making it the most common of the neurologic porphyrias (1). Although its penetrance is only 10-20% (2), acute attacks of AIP are disabling and can be life-threatening. Prevention of acute attacks is the most important principle in managing the disease; however, it requires prior identification of individuals at risk. Because AIP has a genetic basis, molecular analysis for this disease is ultimately the most reliable way to identify gene carriers. More than 130 mutations in the porphobilinogen deaminase gene have been characterized to date (3). The majority have been restricted to a single family, or at most a few families, and no mutation accounts for more than a small percentage of all cases. With the exception of selected geographic areas where single mutations predominate (4,5), testing for known mutations in a patient who has not previously been investigated is likely to be negative. Molecular analysis therefore requires an efficient strategy for finding the causative mutation. Denaturing gradient gel electrophoresis (DGGE) has been used by several groups to screen the exons and flanking intronic segments of the porphobilinogen deaminase gene for variations in the wild-type sequence (6-13). This work has been carried out in European laboratories, and the mutations that have been discovered reflect the molecular defects within that population. By contrast, relatively few mutations have been described in the North American population (14-19). The goal of this study was to further characterize the spectrum of mutations in North American patients with AIP, using a well-established DGGE assay with high sensitivity to identify exons/introns that required sequencing (8). DNA samples were also analyzed by heteroduplex analysis (16) to compare its sensitivity in detecting mutations to that of DGGE.