**2. Interest of chromosome Philadelphia in chronic myeloid leukemia**

• The usual form or standard translocation.

It is the translocation of a distal fragment of the long arm of chromosome 22 (fragment 22q11.2) to the distal part of the long arm of chromosome 9 with recovery of a deleted part of the long arm of chromosome 9 on the long arm of chromosome 22. It is therefore a reciprocal translocation, without loss of chromosomal material (**Figure 1(a,b)**).

Since this date, we defined the standard Philadelphia chromosome as: **t(9;22) (q34;q11) or t(9; 22)(q34.1; q11.21).**

#### **Figure 1.**

*(a) Result of a metaphase karyotype not classified in the R-band. (the circle indicates the Ph1 chromosome). (b) Partial RHG band karyotype of one of our patients: t(9;22)(q34;q11).*
