David R. Witt

Traditionally, DNA used for PCR-based diagnostic analysis has originated from white cells fractionated from whole blood. Although this method yields substantial quantities of DNA, there are some drawbacks to the procedure, including the inconvenience of drawing blood, risk of exposure to blood-borne pathogens, liquid sample handling, and the somewhat involved extraction procedure. Alternatively, DNA for genetic diagnosis has been derived from finger stick blood samples, hair roots, cheek scrapings, and urine samples. Oral saline rinses have also been used extensively as a means of collecting buccal epithelial cells as a DNA source. However, this method still requires liquid sample handling. Herein, we present our results involving the rapid extraction of DNA from buccal cells collected on cytology brushes and swabs for use in PCR reactions, specifically the multiplex amplification of 5 exons within the CFTR gene. The quality of DNA isolated from buccal cells, collected in this manner, has been sufficient to reproducibly support multiplex amplification. Cheek cell samples and the DNA prepared from them as described here are highly stable. The success rate of PCR amplification on DNA prepared from buccal cells is 99%. In a blind study comparing the analysis of 12 mutations responsible for cystic fibrosis in multiplex products amplified with DNA from both blood and buccal cell samples from 464 individuals, there was 100% correlation of results for blood and cheek cell DNA, validating the use of DNA extracted from cheek cells collected on cytology brushes for use in genetic testing.

The Noonan syndrome (NS) is a true multiple congenital anomalies (MCA) syndrome with numerous manifestations. An association with lymphedema has been noted, but its pathogenesis is not fully understood. Nine new cases and a review of the literature explore the role of lymphedema in NS, including its pathogenesis, presentations, and phenotypic effects. Consideration is given to developmental stage at time of onset, chronicity, resolution, and anatomic site. It appears likely that lymphedema is a much more frequent concomitant in NS than previously realized. The major source of lymphedema in NS appears to be a presently undefined dysplasia of lymphatic vessels of unknown cause. Further study of lymphedema may provide an understanding of its role in shaping the NS phenotype. Comparison with other MCA syndromes and animal models is made in this regard. Relevance to prenatal diagnosis and treatment is discussed.