Figure. Schematic representation of 3 breakpoints found in our patients and the suspected mechanism for these deletions.

(A) Nonhomologous end joining (NHEJ), mediated by the formation of a hairpin loop (deletion of exons 4–7; patient 5) and with the insertion of an adenine nucleotide. (B) NHEJ with the presence of a duplicated region and 2 motifs, complementary to immunoglobulin class switch repeats (deletion of exon 4; patient 22). (C) Alu-mediated nonallelic homologous recombination (NAHR) (deletion of exon 10; patient 20).