Bullous poikilodermatitic amyloidosis of the skin with junctional bulla development in IgG light chain plasmacytoma of the lambda type. Histology, immunohistology and electron microscopy]

A 75-year-old patient presented with bullae, poilokilodermatic skin and nail dystrophy as signs of systemic amyloidosis 1 year before an IgG myeloma of the lambda type was diagnosed. The skin lesions appeared at mechanically irritated locations on the trunk and at the tensor sites of the extremities. Histology showed a subepidermal blister and necrotic keratinocytes in the epidermis. There were amyloid deposits in the papillary dermis perivascular, and in the deep dermis around eccrine glands and in arrectores pilorum muscles. Polyclonal antibodies allowed classification of the deposits as amyloid composed of lambda light-chain immunoglobulins. Electron microscopy revealed globoid deposits of non-branching filaments typical of amyloid. The blister was formed at the level of the lamina lucida, with the lamina densa at the base of the bottom of the bulla. So far, junctional blister formation in bullous amyloidosis of the skin has been described only once. Our case is the second report of this blister type, and to our knowledge the first published report of a junctional blister in myeloma-associated systemic amyloidosis.