Hyperkeratotic spicules are a rare disorder that has been associated with different types of malignancies. An association with multiple myeloma raises the question of a relation between the monoclonal component and skin manifestations. We describe hyperkeratotic spicules in a 61-year-old man with a monoclonal gammopathy of undetermined significance. Immunofluorescence and immunoelectron microscopic findings demonstrated the deposition of the monoclonal immunoglobulin at the dermoepidermal junction. Our findings support previous reports that the association between hyperkeratotic spicules and monoclonal gammopathy is not fortuitous and may be related to particular properties of the monoclonal immunoglobulin.