Infact, a homozygous 2064 bp genomic deletion on chromosome11 covering the 5′-region of the TRAF6, RAG1and RAG2 genes (RAG proteins are necessary for B- andT-cell receptor recombination and for the survival anddifferentiation of these cells) was identified in two siblingpatients with osteopetrosis and severe combined immunedeficiency (SCID) by chromosomal microarray analysis.This genomicdeletion covers the region above exon 1 andpart of the non-coding sequences of exon 1. Here, RAG2 is linked to osteopetrosis.