Treatment of Systemic Mast-Cell Disease with Cladribine

To the Editor: Cladribine (2-chlorodeoxyadenosine) is a purine nucleoside analogue with activity against various hematologic cancers.1 Because mast cells are derived from hematopoietic stem cells,2 we evaluated the therapeutic activity of cladribine in a patient with interferon alfa–resistant systemic mast-cell disease. A 57-year-old man was given a diagnosis of systemic mast-cell disease in 1975. At that time, he presented with back pain due to multiple compression fractures of the vertebrae and urticaria pigmentosa. After treatment with spinal irradiation, the course of the patient's illness was indolent, although he continued to have skin lesions. In 1994, he had an episode of . . .