Novel, activating KIT-N822I mutation in familial cutaneous mastocytosis.

[cutaneous mastocytosis]

We report the rare family in which cutaneous mastocytosis was diagnosed in the father and two children , with urticaria pigmentosa as the only manifestation of the disease . The diagnosis of mastocytosis in the father included bone marrow histopathological and cytological examinations and flow cytometry , and histopathological examination of the skin . In the children , tryptase measurement and skin histopathological examination were performed .Blood , urine , and buccal swab specimens were collected from the family members . HEK 293 T cells were transiently transfected with plasmids expressing KIT -WT and KIT -N 882 I . In addition , Ba /F 3 cell lines expressing KIT -N 822 I , KIT -D 816 V , and KIT -V 559 D mutants were treated with imatinib and dasatinib . The effect of treatment on proliferation , survival , and signaling was determined .Germ-line KIT -N 822 I missense mutation was detected in the affected members of the family . Western blot analysis using HEK 293 T and Ba /F 3 cells expressing KIT -N 822 I isoform showed that KIT -N 822 I constitutively activated KIT tyrosine phosphorylation . In vitro assays on KIT -N 822 I -expressing Ba /F 3 cells confirmed that the N 822 I mutant is resistant to imatinib mesylate . In contrast , a high efficacy of dasatinib toward the KIT -N 822 I -expressing Ba /F 3 cells was observed .We provided evidence that KIT p .N 822 I mutation has transforming potential and can cause a constitutive activation of KIT . In addition , we demonstrated that KIT -N 822 I is resistant to imatinib and sensitive to dasatinib . Finally , our findings support the hypothesis that not only KIT mutations but other additional genetic abnormalities are contributing to more advanced forms of the disease .