Pediatric mycosis fungoides: a study of the human leukocyte antigen system among Israeli Jewish patients

Pediatric mycosis fungoides (MF) is a rare disease characterized by over-representation of atypical clinical variants, with a different prognosis from adult MF. Several human leukocyte antigen (HLA) alleles have been associated with MF in certain adult populations, including Israeli Jews. However, HLA data on pediatric MF as a group are lacking. To evaluate the possible association of the HLA system with pediatric MF, 59 Israeli Jewish patients diagnosed with MF at age ≤ 18 years underwent high- and intermediate-resolution genotyping for HLA class I (HLA-A*, HLA-B*) and class II (HLA-DRB1*, DQB1*) loci. The results were compared with data on 4169 umbilical cord blood units retrieved from a public cord blood bank in Jerusalem and samples from 252 healthy, unrelated Israeli Jewish volunteers. No statistically significant associations were found between pediatric MF and any of the alleles examined except HLA-B*73. However, given the extremely low frequency of B*73 in both the control group (0.1%) and the study group (2%), the biological significance of this finding is questionable. Further subgroup analyses by ethnicity (Ashkenazi and non-Ashkenazi) and clinicopathologic variant (follicular and non-follicular) yielded no significant between-group differences. These results suggest that the associations with the HLA system, reported previously in adult MF, do not hold true for pediatric MF. Thus, pediatric MF differs from its adult counterpart not only in clinical manifestations and course, but apparently also in the underlying immuno-pathogenetic mechanism.