Sézary syndrome managed with histone deacetylase inhibitor followed by anti-CCR4 monoclonal antibody.

A 70-year-old man presented to our clinic with a 10-year history of recurrent pruritic erythema and plaques on his trunk and limbs. Based on the pathological findings and monoclonal rearrangement of the T-cell receptor (TCR)-Cβ1 gene, mycosis fungoides (T2N0M0B0 stage IB) was diagnosed. Despite combination therapy including histone deacetylase inhibitor (vorinostat), the symptoms slowly evolved into Sézary syndrome (SS; T4N1M0B2) over 4 years, with dense infiltrates due to atypical lymphocytes expressing CCR4 developing in the entire dermis. Anti-CCR4 monoclonal antibody (mogamulizumab) treatment was started. After seven courses, the CCR4-positive atypical lymphocytes decreased in the dermis to levels below those seen at the outset of treatment. To our knowledge, there is no previous report of a case of SS managed with vorinostat followed by mogamulizumab demonstrating such a remarkable change in the pathological state following treatment.