Sézary syndrome is a rare type of blood cancer that affects the skin and is classified as a form of cutaneous T-cell lymphoma. It is characterized by the presence of cancerous T-cells in the blood, skin, and lymph nodes. Patients often experience symptoms such as red, itchy skin, hair loss, and swollen lymph nodes. The condition is named after the French dermatologist Albert Sézary, who first described it in the 1930s. Diagnosis typically involves blood tests, skin biopsies, and imaging studies. Treatment options may include chemotherapy, targeted therapy, and phototherapy to manage symptoms and control the disease.