Platelet-derived growth factor receptor-alpha-associated hypereosinophilic syndrome and lymphomatoid papulosis.

Fip1-like 1/platelet-derived growth factor receptor-alpha (FIP1L1/PDGFRA)-positive hypereosinophilic syndrome is a rare disorder with a poor prognosis if untreated and for which treatment with imatinib mesilate is highly effective. A 33-year-old man presented with recurrent papular skin lesions and marked peripheral eosinophilia. Skin biopsy revealed proliferation of CD30(+) T cells consistent with lymphomatoid papulosis (LyP), whereas molecular analysis of peripheral blood mononuclear cells demonstrated the presence of the FIP1L1/PDGFRA fusion gene. As the presence of this gene has important prognostic and therapeutic implications, this report underscores the importance of molecular testing in the evaluation of patients with LyP and peripheral eosinophilia.