We report a case of extensive pityriasis lichenoides exhibiting a relentless course. PUVA therapy and oral retinoids cleared temporarily the lesions but did not really halt the course of the disease. Eosinophilia and hyper-IgE occurred after 50 years of evolution. An agressive medullary CD30+ T cell lymphoma without skin involvement was then diagnosed when pityriasis lichenoides became more extensive and necrotic. The disease was rapidly fatal.