A case of Sweet's syndrome associated with monoclonal immunoglobulin of IgG-lambada type and p-ANCA positivity.

We report a case of Sweet's syndrome associated with monoclonal gammopathy of uncertain significance (MGUS) and positivity for perinuclear antineutrophil cytoplasmic antibodies (p-ANCA). A 65-year-old man patient came to our hospital complaining of remittent-intermittent fever, weight loss, associated with papules affecting all his body and without mucosal or ocular involvement. Histology of biopsy specimens of papules allowed the diagnosis of Sweet's syndrome. This is the first case of this rare syndrome associated both with MGUS and p-ANCA positivity. The monoclonal immunoglobulin, possibly directed to neutrophils like an antibody, may cause both their fragmentation and release of antigens responsible of p-ANCA appearance.