Juvenile myelomonocytic leukemia and Noonan syndrome

A case of juvenile myelomonocytic leukemia (JMML, previously referred to as JCML) in a neonate with Noonan syndrome (NS) is described. The boy present ed with bilateral congenital hydrothoraces, nonimmune hydrops, dysmorphic f acies, persistent thrombocytopenia, and leukocytosis. The diagnosis of JMML was made on bone marrow cell culture studies. Review of the literature rev eals an unusual preponderance of hematologic malignancies, in particular JM ML, among patients with NS. Of 40 NS patients admitted to the authors' inst itution during a 10-year period, there were 4 (10%) with evidence of a mono cytic proliferation, which resolved spontaneously. The authors postulate th at patients with NS may have an increased incidence of myeloproliferative d isorders, which in most cases appears to be benign but may be preleukemic o r even lethal.