Subepidermal bullous dermatosis associated with IgA multiple myeloma: a case report

We describe a case of a 76-year-old man who initially presented with pruritic vesiculobullous eruptions on his trunk and shoulders and was subsequently found to have an immunoglobulin (Ig) A kappa multiple myeloma. Chemotherapy and plasmapheresis led to a dramatic resolution of the skin lesions, which paralleled the fall in serum IgA paraprotein level. However, the myeloma later relapsed, and the resulting paraprotein increase was accompanied by recurrence of vesiculobullous eruptions. The histopathological examinations of both primary and recurrent bullous eruptions demonstrated subepidermal bullae with negative direct immunofluorescence assays. Indirect immunofluorescence test detected neither antibasement membrane nor anti-intercellular circulating antibodies. This is a very rare report of bullous dermatosis with elevated IgA kappa paraprotein that appears before the diagnosis of myeloma, and it is a unique case showing an eosinophil-predominant infiltrate within subepidermal bullae and negative direct and indirect immunofluorescence. As the clinical features and laboratory findings of the bullous eruptions in our patient and the other 2 similar cases were not consistent with the diagnosis of any known bullous disorders, the subepidermal bullous dermatoses might be considered as a novel paraneoplastic entity occurring in association with the underlying IgA multiple myeloma.