Acute lymphoblastic leukemia following severe congenital neutropenia or de novo ALL?

Acute lymphoblastic leukemia (ALL) presenting with neutropenia alone is very rare. We describe a newborn with an early life-threatening infection, severe neutropenia and bone marrow findings compatible with severe congenital neutropenia (SCN). She was treated with granulocyte colony-stimulating factor (G-CSF) with complete neutrophil recovery. Three months later she developed a pro-B ALL. We identified a rare loss of 5'-MLL present at the diagnosis of SCN and ALL by FISH analysis using two different MLL (11q23) probes. Molecular analyses for SCN causing mutations (ELA-2, HAX-1 and G6PC3) and for somatic mutations of the CSF3R gene were negative. The early presence of 5'-MLL loss in bone marrow samples may favor the diagnosis of de novo ALL. Nevertheless, the genetic background for SCN is heterogeneous and a non-described mutation for SCN followed by a secondary ALL cannot be excluded. Further genetic investigation may be useful to gain insight into this rare condition in children.