A 16-year-old man with splenomegaly presented with ascites and bilateral leg eschars. Although he had intermittently elevated absolute monocyte counts, a diagnosis of juvenile myelomonocytic leukemia (JMML) was discounted because of his age and lack of persistent leukocytosis. Detailed examination demonstrated features consistent with Noonan syndrome (NS), including typical facies, growth retardation, a cardiac defect, and a history of a coagulopathy. He underwent a splenectomy where the surgeons encountered a rind of tissue composed of monocytes encasing the abdominal organs. After splenectomy, his leukocytes rose to over 100×109/L with a monocytosis, suggesting JMML. On the basis of the clinical suspicion of NS, mutation analysis revealed a KRAS mutation, which is known to be common to both NS and JMML. Clinicians should have high index of suspicion for JMML in patients with Noonan features, regardless of a patient’s age.
*Department of Pediatrics, Children's National Medical Center, Washington, DC
†Department of Pediatrics, Seattle Children’s Hospital, Seattle, WA
‡Department of Pediatrics, University of California, San Francisco, CA
§Department of Pathology, University of Florida College of Medicine, Gainesville, FL
The authors declare no conflict of interest.
Reprints: William Birdsall Slayton, MD, UFHSC Box 100296, Gainesville, FL 32610 (e-mail: firstname.lastname@example.org).
Received August 17, 2011
Accepted January 3, 2012