Genetic Test Developed for Noonan Syndrome

A prenatal diagnostic test was developed to complement clinical diagnosis in cases where there is a suspicion of Noonan Syndrome.

The most frequent gene mutations associated with Noonan Syndrome as well as other genetically related syndromes is examined in this single test and is recommended where there is increased nuchal translucency with normal chromosomes.

A microarray panel for the molecular diagnosis of Noonan and other genetically defective diseases is available. Fifty-two point mutations are examined that are associated with Noonan as well as a differential diagnosis for Costello, Leopard, and Cardiofaciocutaneous syndromes. The syndromes are similar and their phenotypic overlap may be due to the biochemical relationship of the genes mutated in each syndrome to each other. Genes that are mutated in all three of these syndromes encode proteins that function in the mitogen-activated protein (MAP) kinase pathway.

The test was developed by CGC Genetics, (Newark, NJ, USA), who offers a broad menu of over 1,500 molecular diagnostic, cytogenetic and clinical genomic (Clinical Laboratory Improvement Amendments, CLIA) laboratory tests that cover all the major disciplines of medicine.

Noonan Syndrome (NS) is a relatively common autosomal dominant congenital disorder considered a type of dwarfism that affects both males and females equally. It is believed that between approximately 1 in 1,000 and 1 in 2,500 children worldwide are born with NS. It is one of the most common genetic syndromes associated with congenital heart disease, similar in frequency to Down syndrome. However, the range and severity of features can vary greatly in patients with NS. Therefore, the syndrome is not always identified at an early age and this test would lead to prenatal diagnosis.

In most of the families with multiple affected members, NS maps to chromosome 12q24.1. It was reported that approximately half of a group of patients with Noonan syndrome carried a mutation of the PTPN11 gene at that location, which encodes protein tyrosine phosphatase SHP-2.

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