Noonan Syndrome, Cancer Risk, and Growth Hormone Treatment.

Cancer can occur in patients with Noonan syndrome (NS). Review of English literature revealed that myeloproliferative diseases are the most prevalent, followed by intracranial tumours. There is no genotype phenotype relationship between germline pathogenic variants so it not possible to precisely predict cancer risk in NS, however some PTPN11 variants are exclusively detected in juvenile myelomonocytic leukemia and are not observed in other types of cancer. Among patients on growth hormone, cancer development was reported in seven patients with genetically confirmed NS, and five patients with clinically diagnosed NS. However, information on growth hormone dose, timing, and follow-up characteristics in these cases is heterogeneous. In the light of current data, especially in cases for whom growth hormone therapy is considered, the diagnosis should be genetically confirmed, and the results of genetic analysis should be compared with the cases reported in the literature. Families should be informed about possible cancer risk and in cases predisposing to juvenile myelomonocytic leukemia, early initiation of growth hormone therapy should be avoided.