PD-1 blockade for disseminated Kaposi sarcoma in a patient with atopic dermatitis and chronic CD8 lymphopenia.

We describe a 53-year-old male patient with a history of long-standing atopic dermatitis (AD) who presented with disseminated Kaposi sarcoma (KS). Although he never had received long-term immunosuppressive treatment for his AD, he had a 16-year history of CD8 lymphopenia. Because of his heavily pretreated progressive KS in lymph nodes and soft tissues, we treated the patient using pembrolizumab 2 mg/kg body weight 3-weekly. On PET-computed tomography 3-months after the initiation of pembrolizumab therapy, a solid treatment response was detected in all tumor sites - 6-months later a mixed response was observed. Pembrolizumab therapy for further 10 months resulted in stable disease. Notably, his AD also improved during the pembrolizumab treatment period. This report highlights a rare association between AD and KS that was complicated by chronic CD8 lymphopenia of unknown origin. Even though our patient was immunocompromised, he showed an overall good response to pembrolizumab treatment.