Skin disorders in association with monoclonal gammopathies

Monoclonal gammopathy represents a condition characterized by clonal proliferation and accumulation of immunoglobulin producing B-cells. A variety of skin disorders are associated with an increased level of monoclonal immunoglobulin proteins. These skin disorders can be divided into two groups. The first group represents a direct consequence of plasma cell proliferation. The colonization of the plasma cell clone in the dermis expressed as a deposition of proteins related to the M component belongs to this group for which the pathogenesis is well identified, as is the case for example with AL amyloidosis and cryoglobulins. The second group represents skin disorders such as scleromyxedema and Schnitzler syndrome that are highly associated with an M component, or diseases such as pyoderma gangrenosum and leukocytoclastic vasculitis that are more weakly associated with increased levels of monoclonal immunoglobulins. In some other dermatoses such as pemphigus, bullous pemphigoid, epidermolysis bullosa aquisita, Sezary syndrome, lymphomatoid papulosis, urticaria pigmentosa, and acquired ichthyosis, only presumptions exist regarding associations with monoclonal gammopathies. In this the pathogenesis, therapy and prognosis of the most relevant dermatoses shall be described in order of their degree of association with monoclonal gammopathies, which shall also be discussed.