Diagnosis of ALL secondary to CN.

Bone marrow smears at age 9 (A; severe congenital neutropenia before start of G-CSF treatment) and at age 13 (B; severe congenital neutropenia with secondary ALL). Heteroduplex PCR analysis (C) and characterization of rearranged immunoglobulin and T-cell receptor gene loci were performed as described earlier.5 Sequence analysis revealed a monoclonal rearrangement of the DH-JHtype (D). Figures in brackets indicate the number of flanking nucleotide deletions. Lowercase letters correspond to N-nucleotides.