Diseases of the hematopoietic system often manifest themselves in the skin, and some manifestations are so typical that the dermatologist may be the first physician to detect the underlying blood disorder. More commonly, however, skin symptoms arise in the context of a known hematopoietic disease. This book reviews skin signs and symptoms that develop secondarily to underlying malignant or benign diseases of the hematopoietic system, and mainly built as a clinical text to support the physician in making a correct diagnosis and understanding the significance of skin signs for the prognosis and management of the hematological disease. The malignant hematological diseases comprise approximately 80% of the book, which reflects the spectrum of patients in hematology departments, as well as the experience of the authors. In addition to its pragmatic structure that enables the reader to find relevant information, tables are included for differential diagnoses and cross-referencing the skin sign with hematological diagnoses and vice versa. For each chapter, ample background information is provided to convey dermatologists the essence of hematological disorders. Likewise, to enhance understanding among hematologists, dermatological jargon is avoided and skin signs described in understandable terms, underscoring the patterns of the lesions and key features allowing the non-dermatologist clinician to differentiate one skin condition from another. This book is primarily for the physicians who see adult patients; to achieve consistency and readability, the work is meant as a monograph written by specialists in the field, who collaborate with one another on a daily basis. While not aiming to be an exhaustive reference work, it is built as an intelligible handbook that for the first time covers the cross-section of dermatology and hematology. The audience comprises dermatologists working in an academic or hospital setting, as well as hematologists and internists who manage patients with blood diseases in their daily clinical practice.