Abstract
AbstractThis chapter reviews skin diseases and symptoms that develop secondarily to underlying malignant or benign diseases of the haematopoietic system. Skin lesions may be caused directly by infiltration of the skin with malignant cells (leukaemia cutis and lymphomatous infiltrates) or by paraproteins secreted by malignant plasma cells (amyloid light‐chain amyloidosis, type I cryoglobulinaemia and macroglobulinaemia cutis). A number of skin signs are an indirect effect of the underlying malignancy, such as paraneoplastic conditions or dermatological syndromes associated with haematological neoplasms (Schnitzler syndrome, POEMS, AESOP and TEMPI syndromes, neurofibromatosis, juvenile xanthogranuloma and juvenile myeloid leukaemia). Kikuchi–Fujimoto disease, Kimura disease, Rosai–Dorfman disease and IgG4‐related disease are idiopathic lymphoadenopathies presenting with characteristic skin lesions. Skin infections, eczematous lesions and vasculitis are the most common cutaneous signs of an underlying immunodeficiency. Chronic skin ulcers may accompany different haemoglobinopathies, such as thalassaemias and sickle cell anaemia. Finally, the skin signs of transfusion reactions (acute allergic reactions, transfusion‐associated graft‐versus‐host disease and post‐transfusion purpura) are reviewed. Diseases of the haematopoietic 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 haematopoietic disease.