A 31-year-old man was admitted to hospital with onset of difficulty in walking and urinary incontinence, leading to the diagnosis of Langerhans cell histiocytosis (LCH) which was replacing a thoracic vertebra. Four months after the completion of radiation therapy, he was referred to our department with persistent fever and severe pyogenic ulceration mainly affecting the right-hip. A diagnosis of acute non-lymphoblastic leukemia (ANLL) was made. Cytogenetic studies showed 45,X, t(8; 21), 5q-, -Y. We report this case because, development of acute leukemia after LCH is rare and the literature searched for any cytogenetic study in these kind of cases yielded no data.