The overall age-adjusted incidence of mycosis fungoides (MF) worldwide is around 6–7 cases per 1 million [1]. MF is thought to be a disease of the elderly, as 75 % of cases are seen in the age group of 50–60 years [2]. However, MF can be seen in patients under the age of 35 years old with similar findings and clinical course [3]. MF has in fact been identified in children and teenagers [4]; 0.5–5 % of all cases are diagnosed before age 20 years [5, 6]. In addition, MF is observed more commonly in males than females , with a male-to-female ratio of 2:1 [5, 7]—a finding that is more pronounced in children. In a study looking at juvenile-onset MF, 24 out of 34 patients were male (74 %) [1].

In the United States, the incidence of MF, up until the year 2000, was reported to have increased over time [8], a phenomenon that may be reflective of improvements in diagnostics or reporting. Between 1973 and 2002, an increase in the incidence of MF was found to correlate with a higher density of medical specialists. However according to the Surveillance, Epidemiology, and End Results (SEER) registry data, the incidence of MF appears to have stabilized since then [9].