A novel mutation in PTPN11 in an extremely preterm infant with suspected juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia is a myelodysplastic/myeloproliferative neoplasm with a poor prognosis if left untreated. We report a missense mutation (c.794G>A [p.Arg265Gln]) discovered in the protein tyrosine phosphatase, nonreceptor type 11 (PTPN11) gene in an extremely preterm male infant with a mild Noonan syndrome (NS) phenotype and suspected juvenile myelomonocytic leukemia (JMML) whose clinical course was notable for severe, persistent thrombocytopenia, progressive leukocytosis, and profound respiratory failure resulting in death. This is the first such mutation described in an extremely low-birth-weight infant and the first reported case of this variant in association with both NS and JMML. Neonatologists and other clinicians, who work with preterm neonates, should maintain a high index of suspicion for myeloid neoplasms in patients with unusual, unremitting hematologic abnormalities.